One of the most frustrating experiences in a business is not getting paid. But how do you spot the customers who are going to do the dirty on you? Many small businesses are too informal when giving credit. When you get a new customer make them realise from the start that you do not give credit easily. Make the customer apply for credit and especially ask them to provide two trade references.
It should not be difficult for anyone who pays their bills to be able to supply references. If the new customer is a limited company, ask your accountant to look up their accounts at Companies House. They should be able to form some opinion on how safe a bet they are.