When you're both the producer and the customer service (AKA "freelancer"), it's hard to switch hats. You work all day (and nights) on projects in solitude, answer and send emails, twitter and research. What is easy to forget is that customer service is king! You have to keep that line of communication open! In my years of dealing directly with customers, I've found that their main concern is being kept in the loop with their project. Daily emails, phone calls or even tweets do more to make the customer happy than making a deadline.
I have an invoicing system that I wrote for myself and tweaked it to have an automatic email sent to the client when I posted what was done during the day, and the hours spent on the project. He was happier than a dog in a butcher shop!
When the project is done, call the customer back occasionally to see how the site is going. Ask them what they would've done differently, having used the site for some time now. Give them freebies every once and a while- they LOVE that!
Have genuine interest in the project and their goals to success- after all, their success means your success.
