It depends on what you are trying to accomplish. Some of it has to do with if you are heads up or not, what the board texture is, can you
bluff this person, will they raise us back, what pot
odds do we want to give them, are they calling station or not, what position we are in. Just a few things to think about.
There are lots and lots of good material out there on this subject but it’s important to learn why you are betting a certain amount.