In my experience as a startup founder thus far, you may be over-thinking this one. Your lawyers are a valuable source of information and reaction, and help provide some guidance, but they aren't making or breaking your day-to-day existence as an entrepreneur.
Having just gone through a long selection process to find our attorneys, the combination of things we were looking for:
1) Deferral of fees. There are some reasonable arguments that this can actually be counter to your best interests, but if you're bootstrapping and don't have a big nest egg in the bank, it's hard to choose someone who doesn't
2) Affordable rates. Because even if fees are deferred, you will ultimately have to pay them
3) Relevant expertise. I would argue that this has more to do with startups similar to you (e.g. in your industry) than it does with a particular domain like corporate law or IP. He or she should obviously be able to serve you in diverse areas, or introduce you to the right people who will
4) Personal fit. You have to want to work with these people through formation, fundraising, and negotiations.
Look for them by asking for referrals from other startups in your industry. Local meetup groups for your industry are a good place to meet those people.