One of the biggest post-flop changes I made is double-barreling more often. Say you raise with AQ in MP and get a caller. Flop comes 964 you bet 3/4 pot and are called. Against many players I continue to bet the turn, especially if there was a quick call on the flop. (I know timing calls aren't always reliable, but quick calls on the flop generally try to intimidate you from betting again, so this is just another factor in my decision.) I find that many players will float flops like that with 77, a weak pair, or even just overcards. They likely are thinking "If he missed the flop, he'll give up on the turn. If he has an overpair or strong hand, he'll continue to bet the turn".
Maybe it's just FTP players, but damn, double-barrelling is VERY profitable. It works even more than continuation bets! And the pot is larger since there's another street of betting before it.
Tell me about your experiences with double-barrelling. Does it differ in stakes, sites, etc? Right now I'm only playing Full-Ring NL25 and NL50 on FTP.
edit: I forgot to mention, I've been doing this on full-ring games, not 6-max.