A. When players expect you to.
Insiders Secrets To Texas Hold’em Poker Online by Theo Cage 147
Don’t be the fish. Revealing your playing style can be bluffing in
telltale situations against players who know them. That’s a
common money-maker for the other players. Always consider this
rule before attempting a bluff.

B. When you’ve been caught bluffing recently.
You’ve been labelled as a poor bluffer already. Ride it out. Let
them forget that hand. Start rebuilding a reputation as a straight
player so you can eventually try a bluff again later (and hopefully
not screw it up again)

C. Against a dangerous flop.
If the flop has an Ace, chances are that someone has a pair of aces.
Aces tend to make it beyond pre-flop. Also, players tend to
continue to play their Aces. Don’t bluff against Aces.
You also wouldn’t want to bluff against a flop like K,Q,9. Chances
are someone has something they’ll stick with.

Continued from yesterday…

D. Against lots of players.
Chances are that someone has something that they’ll stick with. By
bluffing in this situation, you just become an agent of that player.
From an odds perspective, this is never worth it.

E. Against bad players.
As much as they love to bluff, they love to catch someone in a
bluff. They’re much more likely to “keep you honest” because they
don’t realize what a money-loser that is. It’s much more profitable
to play straight up in these games. Bluffing is only effective from a
“fear” perspective in this case.

F. You just lost a big hand.
Not only might you be on a bad run, but other players will expect
you to be on a bad run, and will more readily call you.

g. You are in a blind position.
You really have to evaluate the flop, but generally other players
will think you have a poor hand and expect you to bluff.