Many experts have suggested that you buy in for 100 times your average bet, but they are confusing buy-in with gambling capital. When you are a rated player, the pit boss records your buy-in, your first bet and, when he gets around to it, your average bet. If you are a serious player, your gambling capital should be 100 times your average bet, but try to buy in for a larger amount to get a better comp rating. This way you'll get increased comps by playing with the casino's money. When dealers see you tipping they want you back and will treat you better, and give you more comps.
Comps are extremely important.
Try to play at a casino that gives you comp credit for spread, not individual bets. You need to ask the pit boss for the meals or shows after each session, though. They don't come automatically. Finally, you need to keep records of your wins and losses. Carry a small pad and pen and make your entries when you are finished with each session.