Originally Posted by DuckieHo
You need to register and operate as a limited liability company (LLC). Keep your accounts separate and pay yourself from the account. Do NOT mix the account with personal or you might weaken the LLC.
LLC isn't the only option. Sole Proprietorship can also be used. Heres a link to all the business licenses - http://www.business.gov/register/incorporation/
You need to purchase a business license and if you plan on operating out of your home, you will need a document for that as well. I have no idea whats its called unfortunately.
The best things you need to work on is customer service. ALWAYS get everything in written form and signed by both parties. If you are selling any systems, make sure to write down serial numbers. Believe me, this can save you thousands on fraud and theft.
You will also need to consult a business lawyer to make sure you are taking everything legally.
Customers always need a guarantee of some sorts. If you are operating at a shop or a single location. I would charge the customers money if you determine the problem and offer them a solution. If you cannot fix the problem don't charge them any money, they will always appreciate your services more, considering geek squad and most other places will charge money for everything.
Also a way to get customers to come back for more is to do the little things for free or cheap, such as a hard drive comes unplugged, or they need to boot from CD on BIOS.