Say I raise the button to $4 with [6d] and BB calls.

1. Flop comes [5h][4s], pot $8 and he leads for $6. I call.
2. Turn comes , pot $20 he leads out $10. Hero?
3. River comes , pot $40 (asssuming I just called turn) and he leads $20. Hero?

Not exactly sure what to do in spots like this. Do we raise flop or turn, and do we call river? I had been just calling the flop but I guess I'm gonna start raising it and then checking behind on the turn, but is there a more gosu way to play this?

Raise flop check behind turn prolly end up folding river sounds good to me...

There is know "right" answer to this question.

Raise flop (he is more likely on missed paint than pair).
Call turn (or if we can rule out 76 and he has a low WTSD% you could try to take it off him here)
Meh - by the river it's v tricky - you can make a case for fold, call and raise. I probably call as I want to see what he's got (for example medium pair or missed draw) so I can make some notes on him..