The first thing you should do before getting any customers is set up your business. I am not sure what you have done so far, if anything, so you should first determine your business name. Once you decide on that be sure a URL (web address) is available for that name. Your customers through word of mouth will search for you that way.
After that, get a business license, register your business and get a tax ID and open a business checking account.
Next purchase your insurance or at least research it and get ready to purchase right before your first client. You want to have insurance before you start a job. Many businesses will require you to show a certificate before they hire you for the job.
Once you have the guts of the business done, you can start advertising as well as building your website.
Hope this helps!