You market yourself and allow them to contact you. If you cant market yourself then how are you going to do so for the client.
If your really good at your job I would doubt your hard to find if I was in the market for your skill set.
Ask Dr Marie above, I doubt she has ever emailed or phoned anyone spamming for work, she became the must go to person if you were hit by google. She is a very well respected expert in this field. Her prices also reflect that, I know I once asked her to look at a site I was struggling with and she was too busy to look. This is what happens when your good at what you do, people seek you out.
So if you have to resort to spamming then .... I dont think I need to explain.