This game is not really hard, a little time consuming and in parts fustrating, especially Ring Leader and Street Racer Elite Achievements, but for the most part you will get the majority of them while playing through the main game. 

For the love of God, do this in Co-Op, makes it so much easier and much more fun to play. Should be able to get around 700 Points quite easily within a few hours, 5 - 8, but for 1250, more then 15 hours are needed. First of all, the easy ones:

ACHIEVEMENT GUIDE

Take Me To Your Supply Point - 10 points

Unlock your first Supply Point

First one you will get, kill the gang members around a Control Point.

It's Good To Be Connected - 30 points

Unlock all Supply Points

Once all Control Points are yours, there are 15 in total:

Los Muertos has 6.

Volk has 4.

Shai-Gen has 5.

Agency Explosives Expert - 20 points

Bomb your way to a 4-star Explosives rating

Just use explosives, grenades, rocket launcher to kill gang members.

Agency Athlete - 20 points

Run & jump your way to a 4-star Agility rating

Collect the Agency supplement orbs (500 in all) and complete the Roof Top Races (12 in all) to increase your Agility.

Agency Wheelman - 20 points

Accelerate and slide your way to a 4-star Driving rating

Collecting hidden orbs will increase Driving (as well as the others), running over gang members and complete Road Races.

Agency Brawler - 20 points

Punch, jab, kick, and throw your way to a 4-star Strength rating

As it says, punch, kick, jab and throw gang members to increase your Strength.

Agency Marksman - 20 points

Hit your target every time to achieve a 4-star Firearms rating

Kill gang members with any guns, pistol, machine gun to increase your Firearms.

Master Agent - 40 points

Earn 4-star ratings in all five skill areas and then max out your Skills Status meters

Once all 5 skills are at 4 star rating, you will get this.

Roadkill King - 15 points

Mow down and massacre 175 gang members while driving

When your driving around, groups of gang members make great speed humps.

High Flyer - 10 points

Make your way to the top of the Agency Tower

Climb all the way to the top of the Agency Tower building, there is 1 that is taller then the other 2, do not attempt until you are 4 star Agility, makes it easier, for those who have not done it before:

Start, the Agency Control Point in the garage, turn around behind you and jump to the outside, jump up to where there maybe 3 guards standing (small building on the your left). 

Turn around and jump to the big building that is closest to the control point (right near a roof top race), use the ledges to scale the building. You will come to the first 'circular' concrete platform joining the 3 buildings, you now have to use the window ledges to continue your way up, these will turn into more concrete ledges. 

You will now reach another 'circular' concrete platform joining the 3 buildings, you can not reach the next lot of ledges. Run around the building to the right, follow to the left where you will see a small 'metal' platform on the side off the other building. Use this to reach the next lot off ledges, you will come to more smaller 'metal' platforms leading up, keep jumping between the platforms to see an 'alcove', jump in, up the stairs to a door leading to the back side. 

Go right, look up to see another platform, jump up to it, follow around the corner to see some pipes going up the side of the building. Use these to reach the top. Ha! Did you think that was it? Look to your left, yep that is where your heading, to the top of the largest building.

Look to your right to see a slightly higher building, get a run up and jump to the platform, run around it to cross to the larger building. Again look up to see another platform above you, jump up, run down through the doors and go left, there are pipes again going up the side of the building, use these to reach the top. Done!

Well, since your up here...

Base Jumper - 10 points

Jump from the top of the Agency Tower and land in the water below

Now jump off, left-corner is the best bet to make the water below, again, I would not attempt until you are 4 star Agility.

Firing Squad - 15 points

Fire away - shoot and kill 500 gang members using firearms

Pretty easy, just use guns to kill gang members, you will get it going through the Campaign.

Bare-Knuckle Brawler - 15 points

Kill 150 gang members with your bare hands (or thrown objects)

Pretty easy, just use kicks and punches to kill gang members, do early in the game while your in Los Muertos, easier.

Mad Bomber - 15 points

Show your explosive personality - kill 500 gang members using explosives

Pretty easy again, use grenades and rocket launcher to kill gang members.

Untouchable Agent - 15 points

Kill 200 gang members without dying yourself

Try to kill 200 gang members without dying, kill from a distance, like up on roof tops.

Body Juggler - 20 points

Use explosives to keep a body up in the air for 10 seconds

Easy enough when you get the "Firefly" as its a 'homing' rocket, kill a gang member up on a roof top, throw straight up and lock-on, fire 2 - 3 rockets at the body to keep it in the air for 10 seconds.

Driving High - 10 points

Achieve a height of 115 feet or more in a vehicle

When you get to 'Garcia Point' Control Point, turn around to see a big statue, jump in one of the cars and drive to it, inbetween the statues feet works.

There is a video of this in our glitches section here.

Car Juggler - 20 points

Use explosives to keep a car up in the air for seven seconds

While you are getting the Driving High achievement, jump out of the car, pick it up and throw straight up, lock-on with the "Firefly" and fire 3 - 4 rockets to keep it up in the air for 7 seconds.

Los Muertos Intel Master - 10 points

Locate all Los Muertos dossier targets

You will get this playing through the Campaign, just locate all the Los Muertos bosses.

Volk Intel Master - 10 points

Locate all Volk dossier targets

You will get this playing through the Campaign, just locate all the Volk bosses.

Shai-Gen Intel Master - 10 points

Locate all Shai-Gen dossier targets

You will get this playing through the Campaign, just locate all the Shai-Gen bosses.

First Blood - 10 points

Eliminate the first of 21 gang bosses

After you kill the first boss, you will get this.

Los Muertos Cleanser - 20 points

Murder Los Muertos - kill all Los Muertos gang members

After all Los Muertos bosses are killed, you will get this.

Volk Cleanser - 40 points

Eviscerate the Volk - take out all Volk gang members

After all Volk bosses are killed, you will get this.

Shai-Gen Cleanser - 50 points

Assassinate Shai-Gen - kill all Shai-Gen gang members

After all Shai-Gen bosses are killed, you will get this.

The Trifecta - 50 points

Wipe the city clean by taking out all members of all three gangs

You will probably get this at the same time as Shai-Gen Cleanser achievement, all bosses are dead.

Repo Man - 10 points

Commandeer 100 gang-controlled vehicles

If gang members drive past you, pull them out and drive away with their car, you do not have to drive far, just enough for the game to know. Do this 100 times.

Confiscator - 40 points

Impound all flagged vehicles and store them in the Agency Garage

But sometimes, when you commandeer a gangs car, see if its on the list, take it back to the Agency.

Airtime Assassin - 10 points

Shoot and kill 5 gang members in a single jump (while airborne)

With the rocket launcher, find a group of gang members, fire the rocket (or 2 to make sure) right near them on the ground to kill them all, I found jumping from a big building to a smaller one to give me more airtime worked better.

Shot-putter - 10 points

Throw any object (other than a grenade) 205 feet or more

Quite easy, after you have killed General Cowell in Shai-Gen, you are at the very top of his building, grab a chair, jump up onto the big glass dome, then simply jump straight up, aim about 45 degree angle and throw the chair. Wait a few seconds. Another way from our glitches section.

Global Impact - 15 points

Kill 15 gang members using the Observatory Globe

This one is not real hard, just tricky, the Globe is at the Observatory in the Volk, behind the Quarry where you fight Olga Romanova, to the left off the entrance / exit for the Agency.

Chain Banger - 10 points

Blow up 100 explosive objects in 60 seconds

This one is actually easy, near the Social Security Control Point there is a big beach with a wooden wharf leading out to a building, this building is surrounded by barrels, there are more barrels near the start of it. 

To get this, fire a rocket at the barrels at the start of the wharf, next run out to the building so you can see the barrels, fire a rocket at them, run back to the first lot and fire another rocket, run back to the building and fire another rocket. Repeat for 60 seconds, the game will replace the barrels when they are out of sight, that is how I got it.

Body Armor - 10 points

Use the Harpoon gun to attach 5 gang member corpses to a single vehicle

You get the Harpoon Gun with Downloadable Content, after you have killed some gang members, pick them up and throw at a car, quickly switch to the harpoon gun and pin them to it. I did 2 on either side and 1 on the front.

Double Trouble - 10 points

Double your fun - complete your first mission in Co-op mode

Easy done, this game is better in Co-Op anyway.

Tag Teamer - 40 points

Partner up and complete every mission in Co-op mode

Get this one after you get the one above.

Pack Rat - 10 points

Complete any Stockpile mini-game in Co-op mode in fewer than 2 minutes and 30 seconds

Object is to collect 100 white orbs in under 2:30, can be found by looking for a white marker.

Front Flipper - 20 points

Execute two forward flips in a single jump in a moving vehicle

See Hazardous Hangtime achievement.

Flippin' Crazy - 20 points

Execute 3 flips of any type in a single jump in any vehicle

See Hazardous Hangtime achievement.

Hazardous Hangtime - 10 points

Execute a 6-second jump in a vehicle

The best place to do this one (and the previous 2 achievements) is on the road out the front of the building where you fight Rodrigo Alvarez, the sharp corner near the tennis courts. On the other side of the road is a large rock, if you hit this heading towards the beach, it will launch you high enough to clear to rocks and land near the beach houses. Use the 'Buggy' as it has better control in the air.

Timed Stunt Driver - 20 points

Execute six car stunts in 60 seconds

See Stunt Driver achievement.

Stunt Driver - 20 points

Successfully execute five car stunts - front & back flips, barrel rolls, a long jump

Team this one up with Stunt Driver, best place to do this is in the building where you fight Rafael Diaz, it is basically an indoor speedway, use the small jumps to do a stunt as you go around, again use the 'Buggy', easy. You do not have to do them all in the one jump of course!

They are the easy ones, the rest are just time consuming to complete, not hard, just time consuming.

Orb Hunter - 50 points

Collect 300 Hidden Orbs

Use this map for all Hidden Orbs. Credit goes to Herman Gatevold for this excellent visual map

Free Runner - 50 points

Collect 500 Agility Orbs

Use this map for all the Agility Orbs. Credit goes to Crackdown Wikispaces for the map,

Rampage - 20 points

Wreak havoc in 60-second increments

This is split up into 6 sub achievements:

Cars Destroyed in 60 Seconds: Blow up 25 gang-controlled vehicles in 60 seconds.

Strength Kills in a Minute: Kill 15 gang members with your bare hands or thrown objects in 60 seconds.

Firearm Kills in a Minute: Shoot and kill 15 gang members in 60 seconds.

Explosive Kills in a Minute: Use explosives to kill 25 gang members in 60 seconds.

Vehicle Kills in a Minute: Use a vehicle to kill 10 gang members in 60 seconds.

Tire Pops in a Minute: Pop 20 tires on gang-controlled vehicles in 60 seconds.

You will get all of them as you play through the Campaign, especially when you go into Shai-Gen as the gangs get bigger, the only one I had a problem getting was Tire Pops, until I went to the Observatory on my second play through, there are 4 - 5 gang cars parked in here before you kill all the Volk bosses. With machine gun in hand, shoot all the tires out manually.

Ring Leader - 20 points

Drive through all of the unique Stunt Markers

There are a few markers that are time consuming and fustrating to get, as you drive around they will appear in the air as a purple ring, sometimes there is a 'ramp' of some sort near by, other times you have look around, there maybe a 'ramp' truck nearby. Much much earier playing co-op, get your friend to throw you through the ring while your in the drivers seat, then swap places.

Road Warrior - 30 points

Successfully complete all 14 Road Races

While playing the Campaign, there are 14 road races around the map, look for a purple marker. Adds to Driving skill.

Over Our Heads - 30 points

Successfully complete all 12 Rooftop Races

Same deal, while playing the Campaign, there are 12 foot races around the map, look for a green marker. Adds to Agility skill.

Psych Out - 100 points

Complete all Time Trial missions at the Psychotic difficulty level

From the Main Menu select Time Trials, select the bosses you want to kill. Objective: kill each boss as quickly as possible at the Psychotic difficulty. Easier in co-op.

Street Racer - 20 points

Win every Street Race using any vehicle(s)

From the Main Menu select Street Racing, the objective is to beat each track with a one of the available cars. Personally I think its more like Wreaking Racing.

Street Racer Elite - 150 points

Win every Street Race using all available vehicles

Same as above, expect objective is to beat EVERY RACE with EVERY CAR available. Good Luck! 

However, I have heard of a couple of sneaky tricks you can do to help you, after the race starts, shoot out the opponents tires or blow them up; this could work, though it would be a pain, they will not stop cause you do. Drive back to the Agency and get the Supercar; as soon as the race starts, head to the Agency as fast as possible, then complete the race using it, as soon as you cross the finish line GET OUT. If done right, it will still be there when you restart the race on the track your doing, when you change tracks, you will have to go back and get it again.

Check our glitches section on this.