I kinda do this, I offer my services to people at work and there friends and family, my normal fee is a case of beer though the odd time it is money, only when I do more then 2 jobs in a week though,
I work from home, but have set up and e-mail strickly for repair correspondence ( sp )
I have all my tools needed in a small easy to carry bag, best to be prepared if you want word of mouth to spread around
work bag includes CD's Both Blank and Various Softwares, and drivers
Philips Screw drivers
Robertson Screw driver just incase
Zip ties
knife
floppy drive and hard drive when ever I have one to spare
Clock.
Now one thing I found people liked was my willingness to bring a PC home with me to work on it, for a reduced Rate if I am doing a full reinstall I would much rather do it while I am going to bed then during the day, so I bring the machine home with me and fix it and ignore the hours it took, just charge for the time I am there, ( my time is 2 parts when beer is the payment, under 2 hours a 12 pack, over 2 hours 24 )
learn how to use "non geek software" but have your geek versions ready to give them. eg: know the ins and outs of IE, but be ready to introduce and explain firefox as a fast alternative.
Have Freeware softwares on CD that can replace demo's of shareware programs, offering free software makes you look better