if youre stuck on betting sizes bet 4BB+1 per limper preflop, reraises are 3x the bet (preflop and post) and bet 3/4 pot on flop and turn, half pot river. Once you get some experience you'll start to deviate in certain situations but those sizes shouldnt get you into too much trouble.

Things to think about before betting a different size are how drawy the board are. Do you have an implied odds/reverse implied odds hand. Is there alot/a little left to be bet. Is your hand any good. Other stuff.