As Graphic Designers, we can't help but experience the best and worst issues about our clients. Drop some of your own issues, tips, problems, suggestions and other things about interacting with your customers. This is going to be a nice way to learn from each other's experiences!
I communicate primarily through email with my clients, and my biggest problem is trying to explain a complex design issue like in coding and make it 'idiot proof' in words. I don't know how many times I have to dumb myself down trying to get the clients to understand what I'm saying.
I don't know if there is a solution to this or if I just have to deal with it. Most clients don't know a thing about design (although they think they do) and NOTHING about css/html and want us to explain to them how do make it simple for them to update their own site. It just frustrates me to no end.
As a tip, I'd say keep your words simple when address clients and make sure everything is clear. And also, have a contract because they always try to change things after the fact without paying extra.
Proper communication is always important in dealing with clients. We can never do away with those nasty customers who talk as if they know the process. But you know what, the more frustrations we get from clients throughout our career makes us more challenged in making our designs speak for itself in future projects.