Asylum Getting DNA
When you are trying to get the man's DNA and must follow him, when you get in the room with all the picnic tables go to the right side of the door and stand there. He will walk by time after time until you get all of his DNA. You will then fight him, escape from the Asylum, then move on to the Embassy level.
Asylum: Elevator code
On the Asylum mission, there is an elevator. The code for the elevator is '4747'. You can get the code by talking to Neil Caplain, who is located in one of the padded cells.
Casino: Unknown spotter
After the first save, change into the stealth suit. Go back and crouch behind the bar. Wait a few seconds and the game will say that you have been positively identified and end.
Embassy: Fire alarms
When at the end and you have to turn on all the fire alarms, one is in Basement 2. After you turn on all the alarms you must hurry to the ballroom and fight three men, then find Dixon and escape.
If your health is low and Sydney is breathing like she is tired, get away from all targets and wait for awhile. Her health meter will go back up. This may take awhile.