Don't be so focussed on looking for new business that you forget your existing clients
A sign that you are providing a quality service is when customers come back to you for repeat business. Don't be so focussed on getting new business that you neglect your existing customer base. Keep existing customers informed of new business services, new develoopments... just keep in touch with them from time to time and keep meeting service delivery agreements.
It's a good idea to every now and again go and reread and brush up on service delivery agreements signed between you and existing clients. Just to make sure that you are adhering to the letter of the law with your agreement between you and them, to ensure that you are keeping to confidentiality clauses and respecting what they are asking you to do. This will also help you ensure that THEY are doing what they are supposed to do in terms of their contractual agreement with you. If you find that they are not, a little gentle reminder can be beneficial. Remember, your old clients are the loyal tried and trusted ones, where the new ones, you don't know so well yet.