Your cards and odds
If you own a hand drawn contrary to the one made, you need to decide if it is worth pursuing the draw, and if so, how many bets. This depends on two factors: how much money you have to win a hand that is likely to win and how large the pot is or will take place.
This involves a bit of math: calculating how many stakes you have, pot odds and implied odds. The more players you have (eight or more is a good number) the bigger you can bet and similarly, if the odds are good then it’s best to keep playing.
What impression are you making?
You also need to consider what your betting model tells other players. Inexperienced poker players often make big bets on strong and small with weak hands, but over time this is predictable.
There are two other approaches that might make your opponent guess: randomly change the size of your bet or maintain consistency throughout. Both are intended to make your opponent the most difficult to read, which will improve your chances of bluffing success.
What is your goal?
Ultimately, the amount you bet is affected by the action you want to elicit from your opponent. There are two simple rules to consider here. If your goal is to let your opponent stop, then you want to achieve this with the smallest possible bet. You risk less chips in the event you are called and most players will stop at a smaller bet as often as they did the full bet.
On the other hand, if your goal is betting, the reverse applies. The bet you want to be called is called the value bet, but sometimes you better so the bigger bet is less likely to be called than the lower bet is more likely to be called, since you will earn more from it.