The rules of No-Limit Holdem are very similar to the rules for Limit Holdem, but again the main difference are the betting amounts permitted.
In No-Limit, any player is allowed to raise any amount he or she has in front of him at any time. If the blinds are $1-$2, and the first player to act has $200 in front of him, and wants to put all $200 in (a raise of $198), he is entitled to do so.
Minimum eligible raise
The minimum size of raises that are allowed must always be at least the size of the previous bet or raise. As an example, in a game with $5-$10 blinds, the first player into the pot could not bet a total of $15, because that would only be a raise of $5. The minimum bet in this situation would be a bet of $20, which is a raise of $10.
In the more likely case that the first raiser makes a somewhat larger bet, for example, a bet of $40 (which would be a raise of $30), the next player could fold, call the $40, or raise. If he raises, he would have to place at least $70 in the pot, because his raise would have to be at least as much as the previous raise. The only upper limit on the size of his raise is the number of chips he has in front of him when the hand begins.
Maximum eligible raise
The total amount of chips you have at the table! All games are table stakes.
Players may not buy additional chips in the middle of a hand, but can always (unless they exceed their daily, weekly, or monthly limit) decide to buy more chips in between hands.
If a player bets more chips than you have in front of you, you are not forced out of the hand. You are allowed to call for whatever number of chips you have. If no one else is in the pot, the bettor simply takes back his excess chips, and the hand is played to conclusion without any additional betting. If there are other players remaining in the pot, it is possible that a side pot may be created.