Perhaps this is obvious, but it’s worth saying anyway. The amount needed to get the job done is not always easy to figure out. Furthermore, it’s not necessarily linear either. That is, you can’t think of it like:

"Well, $20 will get him to fold a pair of deuces. $25 will fold treys. $50 will fold sixes, and $100 will fold kings. $200 will fold two pair, and $500 will fold a straight."

Things don’t work that way at all. Finding the right amount is a psychological problem more than anything else. "If I bet $X, what will he put me on, what will he view his pot and implied odds as, and will he see his pair of queens as profitable?" You have to get into your holdem opponents’ heads and see your bets from their perspectives.

Indeed, in Texas Holdem, sometimes a smaller bet will be more likely to get the job done than a bigger one. Obviously, when that’s the case (or even if you suspect that’s the case) then a small bluff is almost certainly a better play than a big one — less risk and higher chance of success.

There’s no formula to tell how much it will take to get the job done. You have to analyze each case separately.

Also recommended:

1. Heads up Holdem Tips