Sell, yes. And if you build excellent client relationships (LOTS of communication and honesty is good) then your clients should keep coming back to you for ongoing work.

Additionally you want your clients to be your biggest cheerleaders and talk you up and recommend you to their associates and friends for work.

You can even offer a referral fee, I've done this, but generally if people like you, they're happy to make referrals without even being asked.

So far all of the advice here is really good.

I'd like to add that you have to inspire confidence to your clients. You have to be sure about your area of expertise or appear to be sure.

I think the most important idea in your head should be "I can do this." or "I can figure out how to do this."

That's a good way to go and sell your services.