And there's always reputations and word of mouth but I find that to actually be more or less on point when it comes to particular niches, like if you need someone who spoke a particular language or dialect, or someone who understood how to cross examine about technology and not have the jury fall asleep on you, or someone who can handle a child witness and someone who can't. It's not that different in the civil context, is it? There was even a prosecutor who was widely known to be susceptible to running himself into Batson challenges and sure enough the first trial I had against him he managed to dismiss every minority in the pool leaving me and the client the only two in the room which was glaring since the jurors began noticing that something was before we even got there. It was moot since we got a mistrial but if the opposing side is known to be generous with free issues to preserve for appeal you'd be on the lookout, wouldn't you? Or am I still overestimating how often civil attorneys end up in front of a jury broadly?
You do meet opponents, but in some fields, not often enough to really know.
In crime, your client would be in the cells much of the time and you could sit at the back of the court and watch lots of counsel do a good or bad job.
Of course even the civil bar do get to know each other in the way that commercial transactional lawyers - which is what I do now - don't have as much opportunity to do. I am typically dealing with commercial organizations all over the world. Too many lawyers to get to know.
People often ask me for recommendations of a lawyer outside my field, or indeed in my field if I can't help them because my firm is conflicted or for some other reason. The thing is I don't personally use lawyers, so I have only the vaguest idea. I can tell some things from firms' reputations and their websites, but even for me it is a hard call.
And the law firms I have most experience of in practice tend to be the ones which I would go out of my way to disrecommend :-).
So I agree, that is a problem. Particularly for litigation. Unless you are doing litigation a lot - which is likely to be bad news for you - you can't get experience of a lawyer and decide that you like them. Word of mouth is also rather less useful.