Road Cycling - Professional bike fitting

My lower back is killing me after I changed my handlebar position, and I'd like to have a professional fitting done. Is there anything I should look for when searching for fitters? Things like equipment, method, accreditation?
Also, If I change my saddle after the fitting, will I need to get refitted? Or is the angle of the saddle what's important? The saddle can always be moved back or forward to test for the perfect position.

Go to the fitter as educated as possible. Read up as much as you can on frame geometry (ie, effects of different seat tube angles, etc). Also have a clear purpose for the bike (cruising, racing, touring, etc.)

Make sure you know a about various riding positions. The more you know the better....it will also make the fitters job easier.

You don't want to mess this up (because you can't change it later). If you and your fitter work together you will have an enjoyable bike that works perfectly with your anatomy.

Doing your homework here pays more than any other component. It may take a while so don't be in a rush either.

Hope you understand that there will be a charge associated with a professional fitting that some/none of will come back to you unless you buy a bike from the establishment (and are willing to pay this). One of the most recognized is the NECA (New England Cycling Academy) Fit Kit, and they should have a certified tech who does the fittings. There are actually a number of formal methods of fitting a bike (one is Serotta, another is Spinscan, but you'll generally have to find a shop that offers them first). You'll want to call around some of the better known, higher-end shops in your area to see if they have something like this. Ask them if they fit custom bikes, what kind of experience the person who does the fitting is. Perhaps if they fit mainly tri-bikes, and you're not a triathlete, maybe that one isn't for you. Still, the inevitable question that will come up is, "how does it feel?". The point is, if you haven't had a bike that fits you before or haven't done a lot of riding, you may not have given this enough thought. You'll want to do some reading first, then some experimentation before you decide that this is necessary. Maybe adjust the fore/aft position or height of your seat, maybe even consider another stem. Unless you've already done some of this, go to Sheldon Brown's site or Peter White Cycles' site and read what they have to say about bicycle fit. Try to self-evaluate what you read, see how your bike fits applying that criteria. At least this way, when you do go for that fitting and the aforementioned question comes up, you'll have a more informed and thoughtful answer.

Good luck :)

You forgot to mention that dyno they can use ...If you can't put out >2000 watts tell the tech he needs to work harder on finding you a good combination!!

Also, If I change my saddle after the fitting, will I need to get refitted? Or is the angle of the saddle what's important? The saddle can always be moved back or forward to test for the perfect position.
1. No, but you can always measure the distance from the bottom bracket to the top of the seat at your most comfortable position and have any seat you get dialed in quickly.
2. Yes, it's important to always have the saddle at a level position, not angling down or back...
3. Yes, it can and you will want to experiment with this, as it will change your reach distance to the bars and your pedaling position.

Good luck :)