Was rambling on in IRC and thought I'd copy/paste this here for mass beginner consumption:

<spoonitnow> Suppose you're in some hand about to bet on the turn, you're out of position, where your opponent needs 4:1 implied odds to call some draw with
<spoonitnow> The pot is $10 and you have $20 behind
<spoonitnow> You both have $20 behind*
<spoonitnow> The total amount he's going to win is the $10 in the pot and the $20 behind for $30
<spoonitnow> So if you bet $5, he's getting 30:5, if you bet 10, he's getting 30:10, if you bet 15, he's getting 30:15, and whatnot
<spoonitnow> So say you bet $10 and plan to pay off his draw every single time he hits
<spoonitnow> He's only getting 3:1 on his call, and he needs 4:1 to break even, so you're making money either way