Do you prefer a new or a vintage instrument? In a music store, sit down and play several of both. You'll quickly gravitate to one or the other. If you don't play yet, bring a friend who does, and weigh his/her reactions as well as your own. A good piano has a life expectancy of ca. 50 years, and vintage pianos which have been rebuilt can last another 50 years or more. This investment may outlive you.

Are the wood and finish of the case important to you? Most people buy a piano more for its case than its tone. If your budget is on the low side and you're serious about learning to play, opt for sound quality over looks.

Regarding vertical (upright) pianos, the best sound is generally obtained from the instrument with the longest strings, all other things being equal. So choose a vertical that stands tall. If you are in the market for a grand, length matters, but it requires space in your home. Some studio verticals actually have a longer "speaking string length" than baby grands, and thus produce a superior sound.

Japanese pianos, such as Kawai or Yamaha, are known for their dependable level of mid-range quality. Chickering, Baldwin, Knabe and numerous other makes can be extremely good with more individual variation.

Steinway, Bosendorfer, Bechstein, and Mason & Hamlin will be pricey, whether new or used, but they will better retain their value as investments over time. Notice that Japanese, European and American pianos are characterized by different qualities of sound: tighter-more focused, darker, brighter, deeper.

Individual pianos have their own personalities too. Minor variations in thousands of individual parts and the way they stabilize over time, plus the finishing (voicing etc.) pianos receive in the store after leaving the factory all have an effect. With older instruments, I often wonder if all those years of Chopin and Brahms have made them mellow.

Even though a piano may be in good condition, old or new, it may not be a particularly good piano, regardless of price. Buying a piano is like buying a used car; we all drive, but rarely have the expertise to judge what's "under the hood". A piano has ca. 12,000 parts under the hood. So when you find a piano you like, have a piano technician check it out for you before purchasing. An excellent detailed resource for more information is Larry Fine's The Piano Book.