Question About Error Codes

I have notice that alot of people here post error codes that really seem to help to find problems.
1. how do you find these codes? I it a hand held computer that you can buy at a local automotive store ?

2.If so which one would I buy and how much do they cost, also what is the best one to buy?

3. one more question , where would you plug it in?

Thanks again for all your help here guys, Ive saved alot of money by just reading some of the posts here and fixing problems myself, it's amazing how so many of us have the same problems with the same vehicle.
I guess it's a good thing at least this way we dont have to spend a crazy amount of money for someone to tell us to top our brake fluid off....

Don't know about hand held computers, but here is one option; CarChip. Helped me and doesn't cost that much.
http://www.davisnet.com/drive/products/carchip_products.asp

Thanks

Apparently Autozone reads them for free. I live in Canada and we do not have autozones and everyone seems to want at least $50 to read them. I boutgh a code reader from Canadian Tire (Big chain in Canada) for $200 Cdn. It reads the codes from any car that is OBDll compliant (1996 and up).

I think it has paid for itself over and over again.

www.codereader.com

There are better ones on the market but I think this one was good value for the money.

oh................it plugs into a port that is somewhere on all of the OBDII cars. They are a universal connector and on mine it is under my dash.

me again.............lol

I suppose I should add that getting the codes read is step number one for all emissions and CEL related faults.