The online legal researcher. The one whose non-lawyer friends know better. The one who wants updates daily. The one who wants to double-check your work. There are a lot of kinds of irritating clients out there, and while any one of these people might be tolerable, there may come a point where you just can't stand it anymore. You're going to have to quit representation.
How to do it? Well, there's the ethical way, which is heavily circumscribed. Then there's the tactful way, for which there are no state rules.
So what's the best way to go about firing a client?
Refer The Client to Someone Else
This one's kinda mean, but kinda not mean. Your client really does have a legal problem, right? So it's not fair to the client to just dump him or her off on the curb. On the other hand, you just can't stand him anymore; you've told him five times that the statute of limitations bars that one claim he wants to bring, but he just keeps insisting that you should be able to do it ("and my Great Uncle Felix had the same problem, and his lawyer fixed it, so why can't you?").
The best solution is to refer the client to someone else, maybe even someone more specialized in whatever the client's problem is. That way, you have a good excuse: "You know, Johnny Johnson down the street is even more specialized in aquatic torts than I am!" This tactic is especially useful early on in the representation.
Fire Clients Early and Often (Actually, Just Early)
As time goes on, it gets harder and harder to ethically fire a client. Generally, you can do it freely as long as you're not in court yet. Keep documentation of what's been going on; if the client starts habitually doing or saying things that are actually interfering with representation (like not returning your phone calls or habitually showing up late), make a note of it.
It's better to give more advance notice of termination so the client isn't prejudiced. So once it becomes apparent that this client is the type who's not going to be cooperative, send that termination letter.
Get Permission from the Court
Generally, at a late stage in the game -- like, just before a trial -- you need to get permission from the court to substitute counsel. This might involve a hearing, and even then, the court can still decide it's in the best interest of justice not to substitute new counsel. Keep in mind that a court, at this point, won't substitute counsel just because the client's annoying; it's got to be so bad that counsel and client have such opposing goals that they can't get anything done anymore.
In most states, however, you can still stop representing the client if you can assert that you'll be unable to continue providing competent representation.
And the best way to deal with difficult clients? Thorough intake. Don't hire a client who looks like he or she is going to be a problem.