help against a LAG

[Navers]

This was originally posted in the poker theory foruum but I was told that Mr. Schoonmaker and the people who hang out at the psychology forum could answer my question:

I play my friend headsup winner-take-all for small amounts of money. The problem I have playing is that he's very aggressive and bluffs very often. I have slowplayed him and won before but when I'm not catching good cards it can be a while before taking a big pot.

My major problem comes when I have something like medium pair medium kicker and he bets large, something around 4x or 5x the big blind on the turn and river. He bluffs so often its hard to call him down on the turn and river. I'm only comfortable playing my top pairs against him, but I don't get top pair very often heads up.

Whenever I get a good hand (for heads up) like K10 or better, I raise the pot, but if the flop is rags he'll bet enough out on me to force me to fold much of the time.

What adjustments do I need to win more against this type of player? Calling and raising seems fine only in limit hold em, but in NL I tried this and it hurt quite a few times. What kinds of hands do I need to play? What strategic betting adjustments need to be made? Also, what can I do to stop his behavior or in any way alleviate my situation? Any input would be appreciated.