I think about customer service all the time. It's become a legitimate obsession of mine over the years. I love hearing great stories of customer service, learning from companies that value it, criticizing companies that suck at it and trying to build businesses that stand out as a result of it.
The ultimate challenge for a customer service aficionado is running a creative, client-based business. It's truly a marathon. Great customer service is defined not by one or two interactions, but by month after month of consistent communication, met deadlines and work that exceeds expectations.
Like many small web design companies, we depend solely on happy customers. We don't spend any dollars marketing our services; it's all based on referrals. The company literally sinks or swims based on the quality of our customer service. Despite innumerable mistakes and learning experiences, we're still quite successful today because our team spends a lot of time polishing our customer service skills.
Aside from every-day communication, here are 5 things we pro-actively work on to deliver a WOW experience to clients:
Proposals
I believe proposals are an awesome way to deliver WOW, which is why we constantly refine the copy and design of our proposals. The template goes through at least 2-3 major revisions per year. The biggest factor is working to make each proposal unique. Clients can smell a boilerplate proposal from a mile away, so be sure to personalize it.
Also keep in mind that the client will probably not read every word of the proposal. They will scan it and follow-up with questions. So don't get mixed up in creating an extremely detailed scope or including fine print that should be meant for the contract. Simply provide an overview, find creative ways to be memorable and leave them wanting more.

Handwritten Notes
I'm a big fan of handwritten notes and their ability to really create a WOW moment. Most every potential client we deal with gets a handwritten note at some point during the process; even the ones that say no. If the client uses someone else for the project, a handwritten note virtually guarantees they will consider you for work in the future.
Our notes are beautiful letterpress cards and envelopes. We think it's a true WOW to get one of these babies in the mail. Even if the client doesn't acknowledge or thank you for the note, it is still something they don't soon forget.

Professional Comps
Another WOW moment you can create with clients is in how you deliver design comps. Rather than simply attaching them in an email, putting them in a PDF or linking to straight JPGs, we've created a little PHP script that presents them in a really cool way.
Each page is branded with the company name and date. Each comp has a section for people to leave comments on the bottom. We like it so much that we're hoping to open-source the project at some point in the near future so others can use it as well. Until then, here's a little sample of our comp viewer ...

Do a Little Extra
Proper budgeting for a project means including enough padding to account for anything that may go wrong or drag out further than expected. In times when the project goes off without a hitch, it's an opportunity to do a little extra.
"Extra" simply means going over and above what you originally agreed to do. It could mean a couple hours of updates free of charge after launch or an extra round of design changes after the fact. Maybe it means adding a requested feature to their CMS that wasn't in the original scope.
Instead of getting greedy or stingy with a project budget, make sure you use padding to go the extra mile whenever possible. The client will clearly notice when you go over and above the call of duty. If they don't notice, make sure you let them know you are!
Celebrate

Some of our best memories have been celebrating with clients after a project. If they are local we often provide a pizza lunch or bring the whole team by for something fun. For out-of-town clients we have tried a variety of things, most recently sending Nashville's famous Christie Cookies their way.
Often times the method of celebration depends on the client, but it does require thought and planning. It's an awesome way to clear away any tensions that may have developed over the course of the project and express your gratitude in person for their business and continued partnership in the future.
So those are some things we're proud of. What's the coolest customer service interaction you have had in the last six months and why?
PS - I love customer service so much that we're even building a web app to help people manage customer service over email better. You can follow our progress on the app here.