Their's lots of things you can do to help yourself out, many don't even involve guitars at all. But here are some ideas:

-Being on stage can be very uncomfortable, croud withstanding, their's stage lights which means that not only can you not see the croud, but you're HOT. Their's also things to trip on, and if you're especially unlucky, the whole stage sways and bounces in odd ways. I've got to the point where I'm thinking more along the lines of "Where did I set my Red Bull," or "Geeze, if I step there, I'll fall through the stage" then "oh my god... PEOPLE."

-Do anything that puts you on the spot, like public speaking classes, martial arts, etc. That sort of thing will get you used to being in front of people as well as playing out will.

-PRACTICE! You and the rest of your band should be in tune with eachother enough to cover eachother's mistakes. This is an INCREDIBLE confidence booster to not only know that you're good enough to make changes on the fly, but your band can back you up.

-Take into consideration that the only people who will know every time you screw up are other musicians, and they know where you're coming from. So regardless of what happens, make it look like you're doing it on purpose.

-If all else fails blame it on the drummer.
(j/k... You're drummer will beat you if you do that).