On older boards, there is a fine line between just the right amount of heat, and too much, which can lift the printed part of the board off the backing. But it is not to bad when you have done it a few times. When you go to pull the part off the board, keep applying heat to the connections, as you pull....Parts might be hot, careful...
If you are doing carbon resistors, just break them in half with side cutters, then un solder one side at a time...
