Try to hang around the "Sniper Tower". The best weapon is there, along with three sets of body armor. The only level with more than that is the Library, including both the Stack and the Basement. Also, with the big open rooms and lookout towers, it helps to have a gun with a zoom lens, like the AR33, the KF7, or of course the Sniper Rifle.

Stay on the move. The level is big, and your opponents think you're far away. If they ignore you for just a moment, you can sneak back into the action.

Watch out for snipers, who could be at any of the balconies. They often catch you by surprise. I often don't realize that I'm in their range until I see myself in their screen

Also watch out for opponents hiding in the grates or fake walls. You could hide in the fake walls yourself, but in a dead end, you're cornered.