The usual gauge is the amount of experience a lawyer has. While this certainly does not mean that an experienced lawyer will be competent, it should reduce the possibility that your lawyer will make obvious mistakes. Another way is to find out if the attorney has malpractice insurance and what the limits are since insurance companies will not usually insure a lawyer with a history of claims against him. Or if they do insure him it will be for smaller amounts. This may sound funny but it is the most frequent complaint people have about their lawyers.
Service means answering a client's questions and doing so in plain English.
During your first interview with a lawyer or paralegal, see if he or she responds to your questions in a way that you understand. A lawyer who tries to show off with a lot of legal jargon that you cannot understand is not doing his job of keeping you informed. Call for a Free Phone Consultation with an attorney or e-mail for a prompt response.