Personally I make an orbit around the dealer's room first off to see if there's anything I really want and/or any really good deals. Then I head over to the raffle table and buy a few tickets. Then I check out the entries, chat with people etc. Go to lunch. Then look at the entries again, look around the dealer's room. When the show is closing I go back and hit up any dealers when they're getting ready to pack up.
1). Raffles are generally good, about 90% of the time I get way more than I paid for. If you get something you don't want if you're a member of a club you can donate it to your own club raffle- we've had kits no one wanted that have been in circulation for years! If not just look around, if you're an aircraft guy and just got an auto kit find that guy in the NASCAR shirt holding a P-51 and looking dejected. Offer him a swap!
2). You can learn a lot from stuff like 'American Pickers'. If you see a kit you've been looking for twenty years DON'T gush to the dealer the truth and then ask him 'will you take a few bucks off eh?' Tell the dealer that it looks like a nice kit and you might sorta be interested and then ask for a deal. Frank Fritz wasn't the first 'bundler'. Grab a stack of a hundred bucks worth of kits and then ask the dealer if he'll take eighty. And don't shove a hundred dollar bill at him if you do this!!!
3). If the vendor sells the kit you've been looking for twenty years to another guy just as you walk up DON'T punch either of them in the nose!
4). Talk to people, unlike cooks and magicians most modelers are happy to tell you why they did this or how they did that. Great place to pick up tips to improve your own modeling.
5). Don't spend your gas money you need to get home or you lunch money!
6). Sit down and take a rest every now and then. Most shows I've been to have had concrete floors - they'll kill your feet if you spend too much time standing or walking.
Good luck and have fun!