Submitted by: rick
If you've got a man in black on the floor below as you come down in the
elevator, jump towards him when you're about halfway down to his floor.
You'll jump straight up against the floor above and then move forward
into the bad guy as you come down, either killing him or giving you
enough time to duck and shoot. Shoot all the time, especially when you
get at the hard levels. When you are waiting for an elevator, shoot
constantly in the opposite direction. That way, you will instantly hit
an eventual enemy (instead of figuring out how to deal with him AND the
guys arriving with the elevator).
At the end of each level, if you get two red doors at opposite sides
of the building, go down to the basement and teleport yourself back,
instead of jumping back and forth.