County Bar Association
In Pennsylvania, each county has a lawyer referral service that will refer you to an attorney who holds him or herself out as a practitioner in a particular area of the law. If they are holding themself out as a specialist in that area, more than likely, they are more than a "dabbler".
Friends and Family
If you have a friend or family member who used a lawyer and was happy with the service they received, that lawyer may work well for you. However, if your friend used the lawyer for a divorce and you have a criminal matter they are not necessarily the right lawyer.
Newspaper Articles
Many local newspapers have legal columns written by lawyers. In addition, lawyers are often interviewed for newspaper articles. If they are discussing a topic which involves the type of legal matter that you are dealing with, they may be right for you.
Yellow Pages
As odd as it may sound, the yellow pages can be an excellent resource for narrowing down a lawyers specialty. If the lawyer spent money to advertise a particular practice area then they are more than likely experienced in that area.
The Internet
Sites like Avvo and Martindale-Hubbel are good resources for selecting a lawyer.
