Before you start make sure that all of the leads have been disconnected from the computer.

It is strongly recomended to wait at least 15 minutes after turning it off to allow the computer and internal components to cool down.

It is recomended to lay the computer down with the pull tab at the top to allow it to be easily opened.

It is also worth mentioning at this point that for complete safety when working inside the computer that wearing an anti-static band and touching a grounded metal object before starting is good practice.