This is a nice article on how to choose a patent attorney. Patent agents should be considered here, too (a patent agent, fyi, is an individual, not an attorney, who has been admitted to practice before the US Patent & Trademark Office).
Patent attorneys (or agents) are not one-size-fits-all. We have different interests, different areas of expertise, different strengths, different weaknesses. The trick is to find the particular attorney or agent whose combination of strengths, weaknesses, expertise and interests best meets your needs.
Doing a bit of research on the attorney or agent you’re thinking about hiring is simply due diligence. A patent is a major investment; make sure you’ve got someone who can take your matter and do the best possible job with it.
Bear in mind that if your matter involves any representation outside of the US Patent & Trademark Office, you will need an attorney; a patent agent cannot represent anyone (except him/herself) in court.