Start by finding a vehicle (preferably a Banshee) and obtaining a Spartan Laser. Stand next to the vehicle (your body must be touching the vehicle). Charge the Spartan Laser and just as you fire, enter the vehicle. A variation on that method uses an Overshield and a Missile Pod. Person A would have the Overshield, and Person B would fire upon them while they enter (instead of throwing a grenade).