Someone you know has had wood flooring installed within the last 5 years. Ask neighbors, friends, family and coworkers if they were happy with their wood floor installer and if so get their name. Contractors appreciate word-of-mouth referrals and some may even offer a "neighborhood" discount. Yelp is also a great website to find highly rated installers; look for those with a minimum of 3-5 reviews.
The National Wood Flooring Association's certification process validates wood flooring experience and holds their members to high standards of service. You can find NWFA-Certified Installers here.
Most installers will give you a free estimate over the phone or charge a small fee (from $20-$50) to do an in-home estimate. Try to cover all bases and ask as many questions as possible to get a good sense of their experience and knowledge.
Doing price comparisons is vital for you as a consumer, but keep in mind that you get what you pay for. The vast majority of floor installers are honest, hard-working men and women that charge a fair wage and are working to support their families. If they go above and beyond it doesn't hurt to give them a tip at the end of the project.
The best installers are confident in their installation skills and will offer a warranty to back up their workmanship.
If a contractor disparages a certain product and tries to up-sell you a different product, be wary. Sometimes this is done because of a bad experience with a low quality brand in the past, and other times to earn an extra commission from a product distributor. The best way to review a product or brand is to research them yourself online.