When you have SMGs, try to avoid burst firing as it reduces the power of the weapon while at the same time drawing a lot of the enemy's attention. Try to get reasonably close, like 50 virtual metres or so before going full auto.
NEVER STOP MOVING.
Strafe randomly, but continue to move towards the target. If the opponant has a weapon like a sword or shotgun, get a certain distance outside the effective range of the weapons, and continue to blast. Back-pedel (while strafing) when they try to chase after you. If they have a rocket launcher, you're better off finding a longer ranged weapon.