yup, definitely check out petgroomerforums as there are many people who have been to the intergrooms specifically, so can help you much more directly; all competitions are run slight differently to each other, so you're best to get it direct from the horses mouth!!!
Generally speaking the preperation is simply having the groin and pads of feet shaved (NOT the toes! Just underneath the pads!) and it clean around the anus, NO knots or even a hint of a knot, ears clean and plucked, and freshly (that morning) bathed & dried.
You have a set time to be there and set up ready to go, and your dog gets pre-judged; the judge goes over them with a comb and checks your prep (what I listed above) and judges you on that right from the start, they also take note of the growth/length of the coat etc too. You then wait until all the other contestants have been pre-judged, and you all start together. Different classes have different time limits too, make sure you know what yours is and know where the clock is to keep a track of your time!
Then you groom. I was nervous my first time, but once they announced over the loud speaker that it was time to START, then I just went into 'grooming mode' and simply forgot the whole competition; I was busy grooming, and I groom day in and day out, so I knew what I was doing and forgot about the worry of it only moments earlier! lol.
I don't have any info of onsite stuff, cos I'm on the other side of the world, you need to talk to others on the petgroomerforums for that info.
But I will say, that we want to see photos of your before and after work when it comes time!!!!!!!