While lawyers can have a difference of opinion as to what constitutes a bad client, it's likely that there are a few common types of problem clients that can be screened out through careful conversation.
Basically, the best and only way to screen out the bad clients is to talk to them. Beyond having an intake clerk (staff member) fill out a traditional intake form that describes the potential client's case, actually having an in-person, sit down meeting with potential clients to not just talk about their case, but also how you operate, is critical. And though this takes time, it is time well spent as devoting hours to a client that makes you miserable just isn't worth it.
Below, you'll find a few best practices for determining whether your prospective client is a prospective nightmare.
The Overly Nitpicky Client
While lawyers surely know that the old saying, the squeaky wheel gets the oil, is most certainly true, when no amount of oil can stop the squeaking, a good mechanic knows to replace the part. If you're doing your job, you shouldn't have to deal with unreasonably nitpicky clients.
It may be difficult to detect nitpicky-ness, but if a potential client is already telling you how to run your practice better before they're even signed up, you might want to just say thank you and refer the matter to no one else (that you like, at least). If a client seems overly concerned with your note taking during a first meeting, or interrupts you a lot, these are potential signs of nitpicky-ness. However, some of it is actually helpful, which makes it even more difficult to assess if a potentially picky client will become overly so.
The Habitual Late Payer
For transactional attorneys, especially those in small practices, clients that habitually pay late are a scourge to be avoided. Not only do these clients make monthly accounting more difficult, the habitual late payer client can quickly become the non-paying client, which is markedly one of the worst types of clients.
You can try to detect whether or not a client will be a habitual late payer by discussing a potential late fee, or interest rate, provision for unpaid balances (if allowed by your state). While you don't actually need to include these in the retainer, the discussion can help you gauge where the client might fall on the later payer spectrum. And if you want the case anyway, you could consider some form of interest charge for late payment on balances to discourage it.
The Ethical Nightmare
Some clients want things you can't get them within the bounds of your ethical obligations. Having the "goals" discussion at the outset can sometimes help you identify which clients are willing to maintain a level head and which are willing to go overboard.