The point where I am at the moment is that I've been in official business for 8 months and am currently taking college classes (Physics! =P), as well as being a stay-at-home mom. I have not advertised yet, my business has been word-of-mouth so far. My only business customer is a small private school with 24+ computers and I'm under contract with them. The rest has been residential. I do like the idea mentioned about certain fees for certain types of repairs and will look into doing so. As far as the flat fee goes, the way my business has worked so far is that I am able to take the computers home and repair them on my bench. With so little business so far I haven't been inundated with multiple repairs at the same time, so I can be virus scanning while folding laundry lol.
I'm a bit timid about charging by the hour until I am more confident in my repair abilities. It's one of those, 'you don't know what you don't know' situations imo, but I do spend a lot of time reading, learning, practicing, etc.
My proudest self-taught job so far: soldering a new power plug onto a laptop MB. That took a lot of practice learning to solder on dead MB's. Offtopic, sorry.