GO THE EXTRA MILE!
Don't just deliver what you said you would deliver; exceed expectations. Create the WOW factor.
If you're out and about, or browsing the internet and you see something that you think may be of interest to one of your clients (a product, an interesting website or resource, or perhaps a useful business contact), then tell them about it; better still, send them a link or make an introduction.
If you've finished a job for a client, still keep them in mind, and pass on useful snippets of information, relevant to their business.
OK, it's on your own time and you won't get paid for it, but I promise you that it feels really good to do favours - not just for your clients but for anyone, even a stranger in the street - and it can often create a lot of goodwill.
You can't buy goodwill, but you can definitely create it, and get a great deal of pleasure along the way.
Stand out! WOW them! Be Brilliant!
If you employ staff in customer service roles, reading this book should perhaps be an integral part of their induction procedure.