I have never paid for any casino related services for the past 15 years but it does get costly. Your comps are determined based on a number of different factors. The type of casino you visit, 5 star Vegas hotels consider anyone that risks 10K a high roller, Reno 5K.
10 years ago, my executive host in Reno stated $25 bet per hand in Pai Gow for 4 hours will get you a comp room. If you played Pai Gow before then you should know it's a pretty slow game. If you play a game like BJack I'm sure the time would have been cut down dramatically.
To give you an example, I once won 45K in Vegas over a 3 day period from Venietian, everything was comped. On a number of occassions I lost between 5 and 10K during a trip. On those occassions depending on the type of casino some were full comps and some were not. MGM will comp everything if you risk 5K during a weekend trip. Venietian, Bellagio, Winn will not.
To help your chances of getting a higher rating, whenever you raise your bets call a pit boss to verify your tracking. The bottom line is, when you give the dealer your players card(tracking card) and the money you would like to change, the casino considers that the amount you want to risk. Let's say you buy in with 10K and play for 4 hours but you only risk $10 a hand. After the 4 hours you leave winning or losing $200, you would not receive much comps for your time played; however, if you leave with 20K or go broke then you would be comped pretty much everything.
Depending on the casino, the amount you risk you will be assigned an executive host. The first thing I suggest is setting up a marker with the casino, this is not a line of credit but having the casino cage hold your money in the cage. This will allow the casino to know exactly how much you want to risk and you won't be walking around with 5 or 10K in your pocket. :)