Bet sizing, post flop

I see people betting the whole pot, around 3/4ths, and half the pot. what does everyone think the best size is and why? I always bet half the pot up to the river, where I might change things up.

Need more info, like;
game & type (ring/tourney)
Buy-in
etc.

See Sizing your bets in No-Limit

Not to be rude but I did post this under cash games, I am talking about the 6 handed cash games.

I have another question, what is a good bet size preflop, I do 3bbs but i see a lot of people do 3 and a half and sometimes four.

3-4 is fine. I personally do 4bb's as I play 5nl and play a generally strong range against bad players. A bb can make a big difference in how you build a pot. 3.5 is when you press bet pot pre-flop if it's unopened.

Think of it this way.

Say you open to 3bb's UTG villain OTB calls, pot is 7.5bb's. You bet 7 he calls making it 21.5. You bet turn 18 he calls making it 57.5. You can bet the river around 50bb's and come close to stacking someone without a single raise post-flop.

Say you open to 3bb's UTG villain OTB calls, pot is 7.5bb's. You bet 4 he calls making it 15.5. You bet turn 8 he calls making it 31.5. You can now only bet around 30bb's maximum into the river and miss out on a ton of money that will add up in the long run.

The idea of post-flop bet sizing is to plan out what you want to do with the hand. If you want to get stacks in with a set then you're going to need to pot pot pot to get as much in as possible hoping for a raise. Maybe even get a check/raise in there somewhere. If you want to make a medium size pot of around 40bb's with TPTK then you might want to check a street to control the size. It's all about having a plan and picking a line to achieve it.

A further example:

Someone opens to 3bb's, you 3bet to 9 OTB making it 19.5. You bet 18 on the flop he calls making it 55.5. you bet 40 on the turn he calls making it 135.5. You can then bet whatever is left with your stack easily on the river giving him around 4-1 to call. Great for building pots you want to go 3 streets and stack off with like an over-pair or set. If you had checked a street or only bet half pot the whole way, it would be much less attractive to call for villain in lots of spots. Here he basically has to.

I like to use the idea Harrington put out there in his Cash Game Book...."small hand small pot big hand big pot" which goes to what LuckyChippy states...A set (+) is a big hand so you want to get alot in the pot (bet-raise every time). However, an Overpair or TPTK is not a big hand and therefore you do not want to put too much in the pot (bet the flop and check the turn , or check the flop and bet the turn, the point is, TPTK is not a big hand, and contingent upon board texture, you may be bettinig into a hand that has already beaten your Over pair or TPTK. If you do not have it, I would recommend Harrington's Book on the Cash Game Vol 1 and 2 as well as his on-line 6 man cash book. Good luck in your poker endevors

Personally I tend to bet a bit over the pot when I'm trying to make the draws pay to see the next card (or I want them to think that) and between half and 3/4's of the pot otherwise depending on board texture, my cards, and the type of ranges I put my opponents on.