No-limit hold'em is won in the trenches. In shorthanded pots, it's most likely that your opponents have very marginal holdings at best, and your job is usuallyto figure out whether you can make them fold. After all, the board typically won't help you; you'll pair up on the flop only about one third of the time when you have unpaired hole cards.
The rare instances you have a very good hand, you need to squeeze as much value as you can out of it. In the more common instances where you have a decent "but not great" hand, you need to figure out how to get your opponents to put money in with distributions that are behind your hand. And while you're trying to get value, you also need to know when to shut down against foes that have you beaten.
Specific, blanket rules of thumb will kill you at the tables. So, instead, consider these to be some conceptual guidelines to consider when sizing your bets in no-limit hold'em:
1.) When you're the aggressor in no-limit hold'em, you want your opponent either to fold or to call. The size of your bet will primarily be determined by your motivation.
2.) Typically, a range of bets will carry roughly substantial and equivalent fold equity. When betting to make your opponents fold, tend to make the smallest bet from this range.
3.) When you want your opponents to call, size your bets such that your opponents' calling distribution will contain a substantial chunk of hands worse than yours. This may mean that your opponents may be getting marginally positive odds with their pure drawing hands, but this will be compensated by the calls you get from the made hands that you dominate (provided you're good enough not to cough up huge implied odds).
4.) When you have a made hand of some sort, you're usually trying to get calls-but not always. Suppose you have A T, and the board is KQJT. Though some opponents may call you on the turn and the river with something like two pair, this is generally a situation where you're looking to take the pot down immediately against a tricky opponent who's capable of inducing a costly mistake from you on the river when the board pairs or when a club or heart falls.
In poker, you have two primary modes of deception at your disposal when it comes to manipulating betting patterns: 1.) Play the same situation different ways and 2.) Play different situations the same way. Employing these modes of deception may result in you deviating somewhat from these guidelines. But whenever I find I'm being too deceptive for my own good while multitabling, I always fall back on these guidelines to get back on track. Consider these to be the foundation upon which you build the rest of your game.