I have a marketing/advertising strategy of "try anything and everything and see what works"!
I've put up posters of various sizes and wording depending if I'm advertising in a College or Uni or in an Old People's Home (I had an idea that maybe they would appreciate someone coming in to type letter or send off emails for them).
My first "gig" actually came by seeing that the Uni near to where I lived had a "Typing Service" (I found this out because I had a walk around the area, it wasn't advertised on their website) - I then found out their email address from the Uni's website and contacted them.
I seem to get a good number of people visiting my website from the adverts I place on gumtree (which are free).
Much of the problem, when we are new, is convincing someone that we are going to do their job well and professionally.
I was lucky in the fact that the Uni needed a job doing urgently and I was able to type up the 3,500 essay in the evening and email it back to them so it was there first thing the following morning. I took a lot of time over it because I wanted it to be as perfect as possible (!) He was impressed with the standard of work and delivery time and says he will use me again!
I think the majority of marketing is being persistent and just being in the right place at the right time!

Avocet