Repeat customers is the key my dad used to say is the way to build your business. If your customer knows he will be treated with respect and honesty, they will usually come back. That was in the grocery store, but the same applies to the Illustration business. Long time business relationships become that way by the following:
1. Be real. And real nice. Clients have hired you to be the expert. If you feel that there is a flaw in the document layout or a better way to get the message across, it is your job to relay that message. I love emails for this. It gives me a chance to word the idea so that no feelings are damaged. Take every opportunity to compliment your clients on their good taste. It reminds them that they have made the right decision hiring you, and will be more likely to allow you to do your job.
2. Work quickly while retaining quality. Deadlines are crucial to most clients. One of the quickest ways to lose a client is to be late on a project or over budget. It usually takes more time at the beginning of a project, so be ready to put a bit extra in to assure quality doesn't suffer.
3. Be a part of the team. Even if you work remote and never see your clients. There is a lot of pressure in some companies, and good team skills will reflect a happy and productive group.
Being a team player means:
Sharing: Don't be stingy with ideas. The more the better.
Be on time for meetings.
Show confidence, not arrogance.