Always offer a solution to a problem they may or may not have then offer them something for nothing.

"Hi I am the guy who will sort out any problems you may have with your computers, hard or software.
By the way are you aware of TFSA? membership is free and the benefits are enormous, let me show you how to sign up!!
Oh and if you make www.helpful.co.za your home page you get links to all the best and yes most helpful sites!! here is my card with a few links on the back."