The best thing you can do is use table selection and look for spots where there aren't lag's on your left. You want to play them in position. I'm not saying to be a coward or that they can't be exploited, but it's going to be a much easier time for you if you have a tag or fish on your left. Going to battle with a lag, out of position, even if you are good at it, is going to be a high variance, tough situation.
Other than that, I'd look for clues. Is he always three betting the same amount? Is he only three betting 2-3bb raises and doesn't 3-bet 4bb raises? What percentage is he three betting from the button? Is he only doing it to me because I have a crazy "fold to three bet" stat?
Also, how big are the three bets? if he is making large three bets then don't call too lightly. Wait for a quality hand and call his bet or 4-bet him. If he's three betting low, say you bet 3bb and he 3 bet to 6bb, it's probably better to call and play post flop. if you 4 bet, unless you're willing to 4 bet large, he's probably calling because he's in position.