Here are some I found out:
in Mining Pit, you know the bay doors that can "flush" your opponent down. To avoid them from dropping you with their EM Hack, You have to open it, once they are ready to close, walk along the edge (You won't fall over) (I use the right side) and you should be on the other side by the time it is ready to be opened.
In Fun House, the mafia men that shoot at you when you press a button can be avoided when you crouch. Even when you are right in front of them.
Please post some more tips you find helpful in MULTIPLAYER.