I'm a lawyer, and 100% of my practice right now is in the criminal defense arena.
I don’t know a single criminal defense lawyer who operates on a “retainer†basis. I know hundreds of criminal defense lawyers, and all (that are private) seem to operate on a fee-per-case basis. Certainly, you want to have a GOOD one that you can call if you get into trouble. But it’s silly to pay a “retainer†to have the guy show up and agree to handle your case. Criminal defense attorneys leap into action AFTER there’s a problem – I would be extremely distrustful of any criminal defense attorney who demanded payment in advance to handle a case that hopefully will never happen.
Here's what I'd do to find a good criminal defense lawyer in an area. If you know any cops, ask them who they'd want to defend their wives if their wives were to be prosecuted for a self-defense shooting. If you know any attorneys (never mind that they're not criminal defense attorneys - folks know who's good in specialties different from their own, or can find out), ask them the same thing.
Referrals like this are a good thing – folks who know a good professional from a hack generally want to help other folks get the right person for the job, and they’re very happy to make these sorts of recommendations. Often, passing on the name of the person who recommended you will get you treated somewhat better because the attorney 1) has a personal relationship with that individual and wants to please them, and 2) knows that someone is keeping an eye on his handling of your case. I generally try to give folks three names of good people in a given specialty – that way they can pick one that they feel more comfortable with.
Failing this, I'd advise you to start watching the news and papers more carefully. You'll start to notice the same several lawyers defending high-profile cases. Write down the names of three to five of them, and then talk to a cop (go in to a station and ask for five minutes of the captain's time, or go up to a couple of street officers in a doughnut shop) and ask them the question about defending their wives. Get them to rank the names and to tell you if any should just be ruled out.
This should get you three names or so. Many defense attorneys are gun guys - you could call them up and ask if this is the sort of work they do, and if you could swing by to get some of their cards for you and your friends to keep in your wallets. In doing this, you should be able to tell if each one is the kind of guy you'd want to have representing you. No reputable defense lawyer that I know of would charge you for this sort of brief chat, and most will be glad to have their cards out in the world.
I've seen a lot of people advised to contact the Bar for referrals, and I would not recommend this. The Bar is staffed by nonlawyers and their referrals are generally to people who have no other qualification than they are in good standing and they have stated that they are willing to accept referrals in a given area of practice.
The Martindale-Hubble registry is also supposed to be a good way of finding lawyers. I have not found that to be the case with regard to the criminal defense bar. Many (if not most) good criminal defense lawyers don't bother to jump through the hoops that M-H requires (M-H is really a better guide to big firms - use M-H if you need to finde someone to defend an insurance company).
You should remember that it's not that big a deal if you are involved in a shooting and do not have a lawyer's name already. Keep your mouth shut (except to explain that you were in fear for your life - I assume you wouldn't shoot anyone otherwise) and ask for a lawyer - you'll get one.
Again, typically, criminal defense lawyers do not work with the “retainer†system: generally they work on a flat fee basis to handle a case. You’ll want to talk to the lawyer you decide to go with, but it would be most unusual for a criminal defense lawyer to ask you to put a retainer into his trust account against future representation. Probably he’ll just tell you to call him when/if you need him. Essentially what you’re doing at this point is just finding a person who would be competent to defend you in the (admittedly highly unlikely) event that something would ever come up.
Please feel free to PM me if you have any questions about how to find a lawyer.