You could be someone who doesn't mind if (s)he's gets a call late in the evening or at weekends. But you may like having a clearly defined schedule for resolving issues. So set boundaries for doing your job, and insist on it. If the client isn't willing to respect them, feel free to get rid of him.
2) Debating what they pay
Your work is well-done and your prices are fair, but your client is still dissatisfied. These clients drag you down you to poor quality projects. It's difficult to develop your business when you're surrounded by people who aren't ready to invest in themselves.
3) Late payments
It's not a big deal if a client sometimes is late with payments. But if the situation happens again and again, it's time to consider whether this partnership brings you more problems than it's worth.
4) (S)he doesn't listen to you
The client doesn't respect your ideas, refuses changes or thinks that (s)he knows more. This situation can lead to revising your job beyond recognition. Or, (s)he may do everything themselves and then expect you to fix all the problems. These people may pay well, but it's possible that you're going to stop enjoying your job.
Tell them your opinion, finish the work according to what they want, and then move on.
5) No response
A client orders a project, but then doesn't respond to your questions. Slow communication doesn't necessarily mean they are dissatisfied with your work. Most probably you're dealing with an overloaded businessman. So try to get in contact with someone else. If you still don't receive an answer, step down and ask for re-contacting.
6) Lack of respect
Does your client repeatedly re-schedule appointments? It's all right to change plans now and then, but if the situation happens again and again, start billing for canceled appointments. If it still doesn't get better, the client is showing you that (s)he doesn't respect you. This cooperation makes no sense.
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Article source AllBusiness - a U.S. website and community for small businesses