How can I stay awake all night without being caught?

If you're trying to stay up all night without getting caught, I can only assume you're fairly young.  Otherwise, who would be there to catch you? Having said that, the most obvious answer to this question is to be as quiet as possible.

Being quiet when you're trying to stay awake all night, however, is a recipe for failure.  With no distractions, your body will automatically want to sleep.  You could try reading a book to keep you entertained, but it better be a good one or again, you're likely to fall asleep.

If you're trying to stay awake all night for no apparent reason, there are a few things you should consider about sleep deprivation too

1. You're likely to be irritable if you've not slept properly.  This can affect your relationships if you're constantly snapping at people.
2. You're more likely to make mistakes when you're tired.  If you've got studying or work to do, you're less likely to do a good job.
3. Accidents may occur due to sleep deprivation.  It's dangerous to drive or operate machinery when you're tired.
4. Sleep deprivation can lead to an increased chance of illnesses such as heart disease and diabetes.

Personally, I wouldn't try to stay awake all night for no reason.  I actually love sleeping so maybe I'm a bit biased, but being tired when you don't want to be is a terrible feeling.