In Vegas ... its kind of hard. But if you're at a higher end casino like Aria, Planet Hollywood, the Wynn, etc ... make sure to order Scotch, or a hard drink instead of water. All drinks are free, and those shots are like 8 bucks each !!! I must drink 40$ worth of free scotch at every table i play at =)
If your at a local casino like the Bike or Commerce ... just make sure you get a players card because you earn a dollar an hour. You can use the balance for food or stuff from their Gift Shops.
The management has been getting VERY stingy with their comps though ... the only free meal i ever got was when i had to wait 2 hours for a table, and the floorman felt so bad he asked me if i wanted a free meal. Bottom Line ... when in doubt ... COMPLAIN =D
good luck !