Wow....this is sure a popular topic! A lot of great ideas have been posted above, but I think the most important thing was not mentioned.

Getting good results for your customers should be your number 1 priority. Customers who get good results will refer you to their friends and you will succeed.

I have been doing web pages for over 10 years and in our area a lot of newcomers in the business have come and gone because they could not get good results for their customers. So concentrate on results and you should succeed.