Near the end of your stay you can ask host (if you get one) or the player's desk if they can comp anything off your bill. If you have charged the room and/or other things to the room they can comp off the bill. You must play at the properties which are covered by the card you have.
On top of that, do casinos track your players card?
They can only track when you're playing with your card, as that's the only play recorded to their computers. So if you take your card out and then proceed to keep betting, those bets are no longer necessarily captured by the casino's data system.
Even in the case, how much should I gamble for comps? Some casinos that cater to high end players require a minimum of $25 bets to even be considered for comps while other casinos will gladly rate nickel players. My advice is to first call the casino's marketing department and speak to a casino host about table game playing requirements for rating and comps.
In addition to that, how do you get free rooms at a casino?
Rating/Loyalty card from at least one casino.
Can you win too much at a casino?
There is no limit to how much you can win at a casino.