If the advice from the previous post doesn't work, try my trick. I do it all the time at work to get a customers window up until I can get it fixed.
With the Ign on, hold the window switch in the UP position and at the same time hit the door with a rubber hammer right where the motor is mounted. This is on the 'inside' side of the door of course. If you don't want to try this, take a long bar (the lug wrench maybe) and tap on the motor while holding the switch. Just be careful and don't hit the glass while doing this as the glass may break. Another way that often works is to hold the switch and slam the door very hard. If one of these works, replace the motor ASAP. This trick only works 1 or 2 times.
For others reading this, this only works if there is power to the motor and there is no evidence of mechanical problems.
84 500 SEL (307,xxx miles)