The suggestion to get a referral is a good one. However, you may not have that option. So what do you do alternately? Let's consider the answer for an attorney.

The suggestion to get a referral is a good one. However, you may not have that option. So what do you do alternately? Let's consider the answer for an attorney. First, define the legal work as much as possible by yourself. Think of this as "legal pseudo code" that will ultimately be put into the proper legal language. Do your homework: your problem is not new, and some googling will find existing solutions. So before you start making any calls, you should have a pretty good idea of what you need. Now start searching law firms in your area (you definitely want them in the same state, as state laws vary). Check their existing clients (if they name any) and their practice area. Look for significant overlap; they should have done work for companies in the tech sector. Then start making calls or sending emails. By this time, you'll probably be able to select the person you'll use as an "entry point" in each firm. Ask them for an initial interview; there should be no charge for this. Present your problem, and proposed solution. Ask: have they done something similar? If not, get a referral. Now you're suddenly on the inside track. Keep getting referrals and going on initial interviews. As you repeat the process, it will soon become obvious who the top candidates are.