My Suggestions:
1) Buy and read "the Frugal Gambler" by Jean Scott. Jean is known as the "Queen of Comps". She gives numerous tips to get comps both on video poker and table games.

2) Go to http://www.vphomepage.com/

and learn all about full pay video poker. That way can will be playing with an advantage over the casinos (or very close to) and you can get meals and rooms comped.

The previous posts are right in that you must get a card for slots and for table games (you might need a seperate one for each type of game) and make sure you present it every time you play. If you are playing a tavle game, you might want to bet higher when you first sit down and every time the pit boss is looking so you get rated for betting more than you actually did.
You should also ask to speak to a casino host when you get there (or call before you get there!) and you can find out what level of play would give you the comps you want (or you might get comped some stuff up front).
But buy Jean's book and visit the site and you should be on your way!

Paul