+1 what hogz said above.
SV, know first-off that not all BBQ contests are created equal. There are unsanctioned
(often called "back yard") contests, and sanctioned contests. Generally, for the "back yard" contests that aren't hosted by a sanctioning body, most anything goes. You'll see rib only contests, butt only contests, some supply the meats, little or no standards and very few if any judges are trained. Sanctioning bodies are not created equal either. There are different levels of judge training, some not trained much and others go through a fairly rigorous training and must judge many contests before becoming certified. Different meats too. KCBS, having the largest number of contests, does chicken, brisket, pork ribs, and pork butt, on 30 minute turn-in windows, allowing certain garnish, single blind-judged turn-in for each category. Contrast to MBN, which does pork ribs, whole pork shoulder [picnic and butt still joined], and whole hog, with a blind turn-in for each with no garnish, plus 3 independent on-site visits by a judge for each, and then if you make finals you'll get another visit from 4 judges on-site at one time...
My point is this: choose a few contests that you think you'd like to compete in, and
then get to know their sanctioning body. The equipment required/need varies greatly
between them; cookers too. KCBS you'll be cooking a fairly small amount of meat compared to some others, so you'll see very competitive guys cooking on 2 or 3 WSM's, XL BGE's, etc. It's tough to cook a whole hog on a WSM or BGE, so you wont
see many of these types of smokers in MBN cookoffs, perhaps only for someone doing
ribs only, and then you'll see multiples, because most cook 12 - 15 racks for MBN...
+1 what Russ said above too. This may not sound worthy, but trust me it comes from experience. IF you can, see if you cant judge a competition or two. I promise, a picture is worth a thousand words, and in this case not only the picture, but understanding how you're BBQ will be judged, and getting an idea of the level of competition really, REALLY helps. Also understanding who is judging your BBQ plays in to it, because that BBQ that tastes great to you and your buddies late in the evening after having not eaten in a while and after a few brews doesnt tend to work very well in competitions where the judges average age is probably 55, they're judging fairly early in the day, after having recently had coffee and orange juice and perhaps a sausage biscuit or two (and they're stone cold sober).
Good luck!!!