"GO BIG" is slang used amongst the athletes of so-called extreme sports such as wakeboarding, snowboarding, skiing, surfing, and so on. It refers to attempting to pull a trick, and it is an abbreviation of the saying, "If you're going to go, go big." What this means is, you might as well try to catch big air rather than just throw a small trick, because if you succeed, you will have done something really impressive. If you don't, well, it's only pain. This is similar to the saying "If at first you don't succeed, try again."