Just as installing solar panels is a complex, highly professional task, removing panels is just as complicated, especially if they are functioning, solar electric ones. Therefore, my initial reaction is to recommend hiring a local solar installer to remove the panels. Solar panels are worth a lot of money and are not something to just toss off the roof. Even older panels can be refurbished and may have considerable life left in them. However, many older panels were used simply to heat water, so there may not be complex, electrical wiring running through them.
Regardless of the type of panel (these panels are unlikely to be made from newer, thin-film materials as you are looking to remove them), they are usually heavy and working on a roof is always dangerous. So keep safety in mind, first and foremost. Furthermore, make sure ALL power is disconnected to the solar array before attempting any work around the panels.
The most common circumstance in which you would want to remove solar panels would be in a re-roof situation. In this case, your roofing contractor may know someone who can correctly remove the panels. Regardless, make sure to discuss this thoroughly with them. If you had the panels installed, then the best choice is to call the original installer if possible. Otherwise there are plenty of certified solar installers that can answer questions and specifically assess your situation.