Having my bike "fitted"

A bike fitting is so much more than changing seat height and handlebar position...

A professional fit should include there three parts:

Interview:
The fitter discusses any known problems with you (could be a sore back, knee problems, etc. etc.), what type of riding you do (long distance riding, time trial, sprint triathlons, Ironmans, etc.), what you goals are (if you he would only be able to set up the bike for what you are doing now, not what you would like to do next year).

Biomechanics:
The fitter will measure you body, check overall flexibility, check flexibility of specific joint/areas. This combined with the interview gives the fitter enough information to actually put you on the bike

Bike fit:
Here's where the fitter will use you measurements to get you in the most optimal position. Seat height (and tilt) and handlebar adjustments (both height of bar, but also stem length) are done. Plus, cleat position, crank length, etc. Some fitters use computer aided tools to do this (ex. Retul)

Some fitters also offer a followup if needed (the good ones does...) so you can come back within a set time period (could be within a month to 6 months) and work out anything that you have questions about (the reason why should probably shouldn't go back after a week is that the body needs to adjust to the new position).

The benefit of a bike fit is amongst others, better aerodynamics (especially on a tri bike, but also on road bike)(majority of the power you generate to propel forward is used to overcome wind resistance from the rider), more comfort (which means that you will stay fresh longer and get off the bike without pain, this also means that you are actually more motivated to get on the bike which leads to improvements...), and more power (your position will not hinder you muscles to work).

A good fitting is probably in the areas of $150-400, but in my opinion worth every cent.