Reach a height of 1000ft (305m) in Space Program. Place turbo pads in every obstacle spot, use The Wedge, put your character in his first pose (the one where he sits on the driver's seat) and launch your vehicle at max speed. You will eventually get the achievement after a few tries.

Launch three consecutive dismounts at max speed. This only needs practice in using the power wheel.

Do a successful barrel roll and landing. This must be done on the "Scaramanga" level, as the achievement's name suggests. Pick The Wedge, place only one turbo pad on the third obstacle spot and use the fourth steering option, as you can see in the following screenshot:



You don't have to perfectly land on the other ramp, this landing got me the achievement:



Another way to get the achievement (credit to Ti Ex Ex) consists in using the Sasquatch, place a turbo pad on the first obstacle slot, use the second steering option and go almost at full speed:



If done correctly, your vehicle will perform a successful barrel roll:

After completing a dismount, view the replay and lower its speed to 1/16x.

Fully obliterate Mr. Dismount. I got it using the settings I recommend to get the "Look at Him Go!" achievement (so using the Wedge, placing turbo pads on every obstacle spot, going straight with your character hanging from the back of the vehicle).

Get hit by five different NPC vehicles in T-Junction. I got the achievement using the Pink Lightning, steering to the right and launching at max speed, using no obstacles. The Street Slicer is another viable option.

Perform 1000 decapitations. This just takes time, you can get dismembered easily playing on Skid Marks, using The Wedge, placing turbo pads on every obstacle spot, hanging from the back of the vehicle and launching at max speed. You will end getting decapitated several times.

Totally demolish a single vehicle. I have achieved it playing on Froggerer, using the Token Bird, using the first pose for the character, without obstacles, going straight and launching it at max speed. The high number of NPC vehicles increases your chances of getting your vehicle totally demolished.

Lose only a single limb during a single dismount. This achievement is quite easy to get and there are countless ways to get it, my only suggestion is to launch your vehicle at a moderate speed in order to avoid losing more than one limb.

Pull ten somersaults in a single dismount. I got the highest number of sommersaults on Froggerer, try to get bounced by the NPC vehicles without getting ripped apart.

Launch 1000 dismounts. You don't need to fully complete the dismounts, just to start them.

Complete 100 dismounts with the Pink Lightning. The dismount must be fully completed (in other words, you have to wait until the end of the countdown) in order to be considered towards the achievement's completion.

Totally demolish all vehicles (that can be demolished). I haven't found a guaranteed strategy to get this achievement, I can only suggest playing on Froggerer and hope that all those NPC vehicles will do the trick. This achievement is also hard to track, because you don't have any way to know if you have fully demolished a vehicle (except for the first one, which awards you the "Bluesmobile" achievement).

Drive through 1000 turbo pads. You can farm this achievement playing on Skid Marks, placing turbo pads on every obstacle slot and launching your vehicle straight.

Detonate ten mines in a single dismount on Run DMZ. You can use a large vehicle, such as Maximus, Red Hot Engine or Sasquatch to easily get the achievement.

Cut down 100 trees. You will eventually get this achievement by simply playing the game for a long time, but if you're not patient enough you can farm it on Skid Marks: place a turbo pad on the first obstacle spot, mines on the second spot, pick the Red Hot Engine and launch your vehicle:



The explosion will send your vehicle off tracks and it will likely cut down 1-2 trees for every dismount.

Do ten strikes with the Bowling Pins. A really easy achievement to farm, play on The Original Classic, pick the Sasquatch, place a turbo pad on the first obstacle spot and bowling pins on the second spot and launch your vehicle at max speed. Repeat this until you do ten strikes.

Cross the finish line on Skid Marks at 88mph.

First, be sure to set the imperial measurement units in the game options.

Easier way (credit to Mister M16): pick the Komrade, only place a road bump on the obstacle slot right on the finish line, go straight, don't change your character's pose and launch your vehicle at max speed to reach exactly 88mph on the finish line.



I have also found another way to get the achievement. Pick the Sasquatch, don't place any obstacle, go straight and use the first pose for your character (the one where he's sitting on the driver's seat).

You should stop the power wheel like in the following screenshot in order to reach exactly 88mph on the finish line:

Reach a record time on Skid Marks. The record time is supposedly below 9.130, to go as fast as possible pick The Wedge, place turbo pads on every obstacle spot (note: there is an obstacle spot right on the finish line which can be hard to see) and pose your character so that he hangs from the back of the vehicle, just like our friend Jean Claude shows us here:



After that, you don't have to launch your vehicle at max speed (otherwise you'll end up losing a lot of time even before starting), instead you should launch it with an amount of power similar to the one in this screenshot:



Be patient and you will eventually get the achievement.

Play a Steam Workshop level. In order to do so, you must download a Workshop level first.

Open the level selection screen and click on "Browse subscribed levels":



Then click on "Open Workshop":



A browser window will open. Just hover on a level with your mouse and a plus sign will appear, click it:



Now you can close the browser window. The game will update your downloaded levels' list, play any of the levels you subscribed to and you will get the achievement.

Customize Mr. Dismount or a vehicle. On the main menu, click "Customize Character & Vehicle", click "Select Face", "Select Bobblehead" or "Select Vehicle Logo" and upload any image file from your computer to get the achievement.

Nail it 100 times. You can easily "nail it" on Storm Drain, while using the Token Bird. Don't place any obstacle, don't steer and launch your vehicle at max speed. If done correctly, you will "nail it".



Another level where you can easily nail it is Like a Glove (credit to Regi524), using the Ranger, steering like shown in the following screenshot:



Don't use much strength to launch your vehicle and you will "nail it":

Try everything once. I'm not really sure this achievement is working, since I've used every vehicle, used every pose on every vehicle, placed every kind of obstacle, played on every level, used every steering option on every level and used both Mr. and Ms. Dismount without getting it.