The label 'no-limit poker' is a little misleading. While the betting structure does not put a restriction on the amount a player can bet, that player is technically confined by what’s left in his or her remaining stack. You can't bet what you don't have, right? Players can also be limited by game specific rules about stakes, betting and raising.
This said, you have a lot more wiggle room than in limit or capped betting situations, and as such, you also have a little more to think about when it comes to playing wisely and covering your butt. The main difference you'll want to be concerned with is your bet size in relation to pot growth.
In no-limit poker the pot size grows geometrically/exponentially rather than arithmetically. This means that pots can get very big very quickly which is why it's so important to decide off the bat how much action you're willing to give with a particular hand.
The above graphic shows how pots grow in size when someone bets the pot and another player calls. As you add more players, pots grow even quicker, but when people are betting smaller units than the full pot size, the pots will grow progressively smaller - another reason proper bet sizing is so important.
No-Limit Poker Pre-Flop Bet Sizing
It's a common mistake, but many newbies will bet and raise the minimum amounts. As a result, these players are practically begging other (more experienced) players to call them since they’re gift wrapping good odds to see the flop even when opponents have less than stellar hands.
When you are raising pre-flop, aim to raise about three or four times the big blind, plus one for every limper. This will deter other opponents with good odds from calling as well. So, for example, if you are playing a $2/$5 no-limit game and there are two limpers ahead of you, a solid $30 raise should do the trick.
No-Limit Poker Post-Flop Bet Sizing
Post-flop, you generally don't want to be betting any less than half the pot. Ideally you want to bet 3/4 the pot. Reason being that if you are betting any less than that, your hand is losing value and your opponents are gaining the perfect odds to both call and outdraw you.
Make a strong bet, or don't bet at all! Even if you're starting with the best hand, dawdling with minimum bets is giving your opponents the chance to make a connection on several streets of action. What's more, committing to the bare minimum is also telling you squat about your opponent's holdings; for a measly minimal bet, they're going to act regardless. In short, by engaging in this weak play you're effectively screwing yourself on two fronts: you’re slashing your odds while simultaneously depriving yourself of any opportunity to gain valuable insight into your opponent`s hand and the way they play.
Your best bet for no-limit poker is to bet strong, or sit out.