I actually got this idea from the great copywriter Dan Kennedy, and this has probably been one of the most powerful ideas I've ever implemented in my business.
While it's easy to automate tasks like running pay per click that will keep bringing new people to your site, it's important that you actually take the time to take one action everyday that will continue to bring in new customers.
The reason you need to do this everyday, even if you've got more customers than you can handle, is that if you don't do it everyday, it won't become a habit. If it doesn't become a habit, eventually things will slow down, and then you'll need to go into crisis mode to get a new windfall of customers. Then you'll stop trying to get more customers in because you have a lot again, and the viscous cycle will complete.
Here are a few ideas for actions that you can take everyday that will ensure you're attracting new clients:
Article Writing
This is one of my favorite ways for getting my name and services in front of people. I simply write at least one new article everyday and submit it to the article directories. As a way of saying thanks for the content for their site, the articles give me the opportunity to give a little plug for my services and a link back to my site.
Reply To Inquiries
Do you have questions from people who potentially want to give you money? If so, reply to them.
Think Of New Keywords For PPC Ads
If you run pay per click campaigns, like Adwords, then you could brainstorm new keywords for your campaigns. Try seeing if you can come up with 10 or 20 new phrases for your ads.
Make Videos
This is another way to get your face, personality, and services in front of potential clients. Record videos on topics related to whatever niche you're in and upload them to sites like Youtube and Metacafe (I'm starting to become a bigger fan of Metacafe everyday – try it out).
Don't like any of these ideas? Then come up with something that's appropriate for your business.
Just remember that having a waiting list for your services means is a whole lot better than struggling to find customers.