Kurt,

Sometimes these problems are easier to prevent than they are to cure.
It may be good to limit the amount of credit that you extend to a new client until they demonstrate their ability to make timely payment. At least the losses remain at a manageable level.

If I could make a suggestion, you might want to consider having new clients (especially smaller and unknown ones) provide you with a credit application which includes both bank and business references. In the event that you have to sue them, you will know where to go to satisfy the judgment.