When continuation bets fail

[ticks]

I like continuation bets as they make me a lot of money.
However, they sometimes get me into trouble.

It usually goes like this:
I raise 4xbb preflop with AK.
One or two callers.
Flop comes Qxx.
I bet the pot.
One caller.
Turn is a blank, I bet 3/4 pot.
Call.
By the river there are no obvious made flushes or straigths,
so I bet 3/4 again or I check and fold to a bet from villain.

Should I start giving up more often on the turn?
How do you play it in these situations when you are up against a:
a) LAG
b) LP
c) TP
d) TA

I play 25nl 6-max, so we will assume villain is bad to average.
And lets assume stack sizes are the same.
Think I could save a lot of bets if I could get these situations right.

Any suggestions?