Of course you know the answer changes based on the board, the player, stack sizes, and position...

I assume your'e talking about the situation when you're out of position, having to act first after the flop. (When you're in position it's so much easier, if they check to you, then I make another bet on the turn, if they call that one, I slow down on the river. Unimproved overs just aren't worth it.)

When I'm out of position, I've been varying what I do lately when it comes to continuation bets. If you're playing shorthanded, or with decent players (that may attempt to get reads on you) I don't even make a continuation bet sometimes, and fold to the slightest bet from any opponent. This gives them the impression that you don't get tied to a pot and you fold if you don't have anything. This can set you up for more successful continuation betting on later hands. Here are just some general rules that I follow when it comes to continuation bets, assuming your in EP (also assuming your overcards missed)...

-Randomly vary the size of your continuation bets
-A check-behind is almost always a sign of weakness, it may be safe to fire on the next street.
-If any paint comes down, bet into 2 or less opponents, check/fold to 3 or more opponents
-If you hit a draw with 8 or more outs, always bet
-On a board of all rags, uncoordinated, bet into rocks, check to Laggs/calling stations
-If you see players regularly calling continuation bets, then don't make them every time (mix it up)
-Try to determine if a player is on a draw (tough to do out of position, but the board will help) You may be able to continuation bet until the river (some people are just stubborn...)
-If they called the flop bet and there is no apparent draw, either check the unimproved turn or make a smaller bet.