I'd find a reputable LBS and go in for a full fitting. Ask around if you aren't certain about a good place to go. Yesterday I had a very extensive bike fitting done. The spouse is getting a fancy-schmancy custom made bike, and as part of the deal, I got a free fitting, both for my current bike, and the one I am inheriting from the spouse. The guy went through everything from cleat position to how I was pedalling, etc., etc. He also had this nifty bike fitting thing, where he could adjust everything, from top tube length to handle bar angle, to seat angle, and on and on.


And yes, we took pictures, because DH loves to photodocument almost every aspect of our lives...!
The verdict was sort of amazing - my current bike just doesn't fit me. The top tube is way too long, the seat was too far back and too high, the handlebars were too big... it goes on and on. While it might sound kind of depressing (or like the guy was trying to sell a bike - which he wasn't - he knows that I'm holding out until next spring), it was actually quite fascinating. Luckily, many of the problems are fixable (not much I can do about the top tube, but they can move the handlebars around to take up some of the slack).
I pick up my modified bike today, and will go for the first ride tomorrow. I'll report back, but seeing how the spouse rode after his fitting on his current bike, I'm convinced that a professional fitting is well worth it - he was riding much more efficiently, and with a lot less effort/post-ride pain. I just hope it results in me picking up my average speed by a couple of miles an hour!
Melior victus per venenum