1. Every Joke Has A Point
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Regardless of the publicity of a practical joke, it's important to remember that every joke does have some kind of point--whether that point is to make people laugh, to teach them something, or to just break up a mundane day.
2. Embrace Absurdity
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Alternatively, if you just want to pull a practical joke but don't have a particular point to make, then go with the absurd. As Nigel Crowle, a producer for Noel Edmonds and Jeremy Beadle, you should be creating "layer upon layer of absurd situations, build it up, to a climax, which really if you analyzed it make absolutely no sense whatsoever."
3. Know Your Audience
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Make sure that everyone gets the joke. I mean, what's the point if no-one even thinks what you're doing is funny?
4. Be Prepared
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Depending on what practical joke you're pulling, check and double-check that you have all the proper supplies before you launch into it. You don't want to get caught with your pants down--unless that's part of the joke.
5. Push Boundaries
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A good practical joke isn't just something that you do to a friend when he's drunk (well, not ALL of them), but one that crosses boundaries and makes people think--like lines between amateur and professional, art and trash.