Man of Honour
More work than I can handle, is better than not enough work. If it turns out to be an overflow then I will back off my advertising and focus on my customer base, also consider taking on other technicians. As asked, I will not attempt something that I cannot handle or deal with at the time or by myself. I will go away improve on my knowledge of that area and then maybe re-offer the service.
Too much work can result in a poor service which is deterimental to your buniness So get to know your local competitors. Build up a trust with one you so that you can pass on work to each other.. They'll be times when you need advice and support and it works both ways.
Oh and Ccleaner portable... Have this on your USB stick. Imagine that P3 450MHz machine which has never never had a cleanup!