Personally I think anyone who opts to judge a show wants their head examined, they make three people happy and a damn sight more very bitter, not an ideal situation.
I'd pick up on what someone posted earlier about judges knowing what they're looking for and being experienced regarding dogs,
I've witnessed (as others will have) people judging that have been in the dog game twenty minutes, go through dogs like underwear but are considered to be more knowledgeable than your average lurcherman simply because of the volume of dogs they've owned.
All that aside however if you choose to enter you