Quote Originally Posted by Thunder
I know that with 9 cards to improve his hands, the odds are 19% and that Phil likes to work on an 'outs multiplied by 2' ratio to get 18%. So I round it up to 20% (or 1 in 5) and conclude that a bet of $200 would be enough.
This is one of the most misunderstand points of probability vs. odds. If your probability is EXACTLY 20%, you need to bet $333 to give him break even odds. If you're 1 in 5, your odds (against) are 4:1.

You play this 5 times. Each time, you bet $333. Each time, he calls. He's getting 4:1 on his bet. Four times, he catches air, and you win 4 x $333 = $1,333. The one time he hits his draw, he makes $1,333, breaking even.

This is easier from hero's perspective. If hero has a fractional probability of hitting the hand that is 1/3, hero needs to get 2:1 pot odds.

In practice, I like to bet at least half the pot (in the example, $500). Why? This goes back to your suited connector thread. He might have a combo draw. And I play fish, not Lederer. So I want to make sure that they don't have anywhere near the correct pot odds to call, even if they have a few extra outs. Note that even with a Flush/Inside Straight Draw and 12 outs, he would still be only even money. I try to bet 50% of the pot miminum against draws. At my levels, I get assinine calls ALL the time.

Rule of thumb on the river: always bet AT LEAST one third of the pot against draws, and AT LEAST 1/2 the pot if you think it might be a combo draw. And bet the whole pot if you're against a fish who will call it.