A post I made from another thread. These aren't the best tips, but they'll sure help keep you alive and dealing damage.
"Some BA tips:
1.As a BA in maps such as swamp with cover in relatively shallow water with seaweed in it, fly up out of the water, shoot, and fall back in to be more effective at fighting larger enemies. I nearly soloed an un-damaged Warhammer doing this when I was really new to the game.
2. On a low gravity map such as extremity, try to fly a little way above your enemy's head and bombard them with grenades and rockets, just make sure you have enough jet fuel to fly away so you don't go down too.
3. When on a low gravity map, make use of turning direction mid air to keep changing directions to confuse your enemy and get more damage dealt before you die.
4. When playing as a BA and you have a base/group of allies about to be attacked, you can confuse your enemies by crouching on top of a steep hill with a PPC to use the knockback to fall off and recharge before you fly up again. This is a great way to deal decent damage and get points while keeping yourself alive for as long as you can.
5. If you know you're going to die to an enemy, make suicide run using PPCs, grenades, rockets, and heavy lasers to deal as much damage as you can to them before you die. (If you don't die the first run, you may be able to make several more and destroy even heavy mechs with slow rate of fire weapons.
6. When I'm piloting a vehicle, I like to jump out and fly up right as I get hit by an explosive weapon when I'm about to die. Sometimes enemies will mistake you for a flying piece of debris, allowing you to get in a few last shots.
7. If you are extremely careful, you may be able to destroy a lone assault mech by getting on it's shoulders and shooting it with something like a heavy laser. Be careful, though, I've been blown up by my allies doing this. And if you somehow crit the mech when you run out of jetpack power, you're pretty much toast."