Does anyone have any acting tips for how not to laugh while on stage?

The problem is that you keep repeating the same series of events (the lines you're delivering, your stage movements and stances), and each time you provoke the same responses in yourself. Quite accidentally you (and possibly other cast members) have created a little hypnotic response.
It works the same way as Pavlov's famous dogs. You have anchored certain responses to certain stimuli and now, how ever hard you try, you can't stop reacting the same way to that same set of stimuli. To make matters worse, after a while you start to anticipate the giggles, expecting them to come, and sure enough they do.

To get out of this loop you need to over-write the programming with a different emotion. Go over and over those lines and, BEFORE you start feeling the giggles, get angry (you'll probably need any co-gigglers to do the same). Keep going over the lines with anger. Then start letting the anger come of its own accord the same way the giggles used to. Start anticipating the anger the same way you used to with the giggles. When you have got that, start again but this time with immense sadness. Start feeling the sadness before the anger or the giggles and make it INTENSE. Go over the same lines several times. Make sure you get to the stage where both the anger and the sadness start to come of their own accord.

Having done that, you will have three emotions available in response to the same stimuli, instead of just one; this choice will open the possibilty much wider so that when you go back to delivering the lines normally you will be able to choose between them.

It is better to do the over-writing on stage, lit, with as much as possible the same as when you get the giggles. Many things can act as the anchor; the room, the lines, the smell, the sounds. So if the re-write is conducted off-stage it is less likely to work (you get back on stage and the anchors are so strong, you go straight back to giggle mode).

Ultimately it is best if you use as one of the over-writing emotions, the emotion most likely being felt by the character at that time (a bit of obvious advice). The giggles arise not from nerves, but from uncertainty and the associated breathing patterns. It is a psychological response to emotional uncertainty and particular repeated (chained) states. It happens less when the emotions of your character are clear and strong. It can, therefore, be a sign that you are drifting out of the association with your character towards a neutral state. So to avoid it in the first place, stay more firmly in character and be conscious of your breathing.

When I act and I have to laugh, I usually think of something sad, or scary. It makes me stop. I also hold my breath and it seems to work. It also takes practise, it took me a while to catch onto the trick. If you want to see something scary, I got the video for you! Go here: http://www.answerbag.com/q_view.php/86026

The benefits of increasing your in-the-moment, presence (on stage and in life) are infinite.
I begin with that because you're describing something that's an issue of concentration. Where are your thoughts primarily focused when you're on stage; on the task at hand or on other things? Another way to ask the question is FROM where are your thoughts focused? Are you (your consciousness) IN your body, functioning through you (your personality) or are you (your consciousness) outside of of your body observing how interesting you are? It IS "interesting" to watch a driverless car maneuver through traffic but it's not wise or safe. When one's focus drifts on stage, unwanted laughter and many other behavioral "ticks" can arise.

You know that scene in the Wizard of OZ when Toto pulls back the curtain (actually if you watch close enough you'll see that he doesn't pull the curtain back. It's somehow just fastened to his side) ANYWAY he exposes the phony wizard. Imagine that ALL the internal "stuff"/technique you use to fuel and create a stage-worthy character is what lies "behind the curtain". Like the phony Wizard, you only want the audience to see the big, green, floating, disembodied head on fire. You DO NOT (nor cannot, as a professional) let the audience see that your artistic output is resulting from your frantic internal button pushing and lever pulling.

Finally, laughter that's not "about" anything is usually a release of nerves/anxiety or a deep recognition of truth which happens without permission (or participation) from the intellect. YEARS ago I recall being internally "tickled" (as actor, not character) in response to some moment in a play. Laughing would have been ridiculous for the character, not to mention grossly unprofessional. I remember threatening myself that I would have to stop acting if I couldn't rise above the urge to laugh. The urge vanished. I hope you don't have to go that far. Just find more and more ways to increase your concentration (however boring it might seem) on the moment to moment reality of what you're doing.



"Forgiveness is the fragrance that the violet sheds on the heel that has crushed it."
Mark Twain

pretend you're at a funeral.

Yes, it's important that you have a do-able focus, something practical to take your attention away from whatever is causing the fit of the giggles.

Mark Westbrook, a great acting teacher in Scotland has written a great article at http://acting-blog.com/tag/laughing-in-rehearsal/

That should help you out.

I think of somthing sad i dunno i never had that problam

Laughing inappropriately (when it's not in the script)in public is usually a sign of nervousness. Try to forget that there's an audience and that you're on a stage. Look over the heads of the people rather than directly at them and concentrate just on your performance. Doing some deep-breathing exercises just before a performance can also help control nervousness.

Dont look derectly at peaple!for sure.

Acting is believeing, you actually have to believe your the part and the things are actually happening to you. If your in "the zone" then laughing shouldn't even be a problem.

I like to become totally immersed in what I'm doing. Once I am completely memorized, and I can really think about what I'm saying while I'm saying it rather than just trying to remember my lines, I can get really into the character. In doing that I am not thinking about something else that might make me laugh.

http://www.wikihow.com/Keep-a-Straight-Face

Some tips just for that :)