Even within a field as narrow as probate law, there are subspecialties that you should be aware of when searching for an attorney. If, for example, you're contesting a will, a probate attorney whose experience is in malfeasance claims against executors and administrators may not be your best choice.
Some law firms specialize in nothing but probate law. While you can find them in the Yellow Pages for your area, you'll probably have better luck searching the Internet. Web pages allow them more room to discuss things, from their particular subspecialties to their rates.