masking tape

When I painted my van I masked up the two trims around the passenger and drivers doors as they are in good condition. Now after three weeks how do I get this tape off without damaging the paint. It is stuck well. Somebody out there must know of a safe type of solvent or similar to use.
Trevor//

Wax and grease remover, also known as Prepwash or Prepsol.

There are a few reasons tape residue is left behind. The tape has gotten wet, or lots of sun on it, it is really cheap tape, or has been on a long time.l