-Turn on all the valves you find. If any type of guard stands by a valve that is on, they will pass out.
-To defeat riot guards, shoot a shotgun a couple times at the black panel on their backs.
-Use the minigun to destroy the robot guards during the last battle. Try lining the robots up for better results. The force of the gun will push the robots. If they are in line with each another, they will both become helpless.