First you need a mongoose and two people, you have one person drive and the other in the back, and the person in the back needs to have a gravity hammer.
Then when you go off a jump/hill the guy in the back slams the ground on the side/back of mongoose.
You will do flips, spins, and barrel rolls depending where you hit the ground, but don't hit in front or else the guy driving will be toast.
Make sure you have full health because it drains all of your shields.