There are a few very simple do's and don'ts. You generally need two peopel for the procedure.
***Don't use cheap cables! They can heat up very quickly and may burn your hands!***
Make sure both cards are turned off. Connect the Possitive (+) of the battery from the bad car to the Positive of the good car and check the connections. Then do the same from Negative/Ground (-) to Negative/Ground. Start the good car and leave it to tick over for a couple of minutes (usually about 2/3) and try to start the bad car. Have someone stand nearby the good car to remove the Negative/Ground (-) wire from the good car as soon as the bad car starts. The other end can then be disconnected form the bad car. The same can then be done with the possitive cable.
using this method helps to prevent any sparking that could cause the battery to explode.
**Note** As a precaution try not to stand near the bad cars battery as the initial connections are made.