Try not to eat anything or drink anything for about 2-3hrs before you go out...
I have the problem of passing gas a lot... I usally will try to hold in and usally can do it. However sometimes thats just painful. So what Ill do is put my scent killer in one hand and spray my bum good. Let her rip, then spary for a min straight. But hey, its better than getting down from the stand, I still am able to see deer and havent been winded. I wouldnt try this if you can see a deer though. Just try holding it I guess.

