If you have a stable swing, a fitting can help. Not a great swing, but a stable one where similar things happen form day to day. If your swing is unstable, average off-the-rack clubs will probably do it.
At the very least, get a static fitting: This considers things such as flex and length of shaft, lie angle (fairly consistent for most golfers), and grip thickness. A static fitting helps you find clubs that won't hurt your game. Static normally will do the trick for beginners.
If you have never had a fitting, and have a fairly stable swing, you can learn about your swing from a fitting. A fitting will show you what "shaft range" will work for you. The Maltby MPF Shaft Selection tool can give you an idea of which shafts to try. http://www.ralphmaltby.com/265
The Mizuno Shaft Optimizer can pick up certain aspects of your swing. One aspect is tempo - how quick or smooth you are in your transition from "the top" to downswing - can influence the types of shafts that work best for you.
The fitting tools get you into the right "neighborhood." From there, you pick the house (or clubhead-shaft combo) which you like best.