practice in it. don't pick someone who "dabbles" in it. don't go off of just their website...spend a morning at 341 meetings and see who has a lot of cases on the docket and seemingly has the trust/confidence of the trustees. call a chapter 7 trustee's office and ask for a suggestion...they'll probably be bugged by the call but they'll still probably give you a name.

if you happen to be in AZ or CA i can help you out with referrals. if some other state, ask other lawyers you may know who a good BK attorney is and go to them.