I've installed several lights and relocated switches and outlets. When ever I route wire down to an existing switch or outlet, I usually have to cut out a section of drywall near the switch or outlet to get the wire in which results to drywall patches. There's got to be a better way!. Is there a "trick of the trade" that would eliminate cutting into the drywall. Please respond..

The easiest way for me, and the way I did my house was to tape the new wire to the old wire. You are then installing the new wire and removing the old wire at the same time. This can be done by pulling from the room to the attic or by pulling down from the attic to the room. Make sure it's secured well however or you'll be back to cutting a hole to find the wire or using a "fish tape". A "fish tape" is a stiff wire (available at any home supply store) the new wire connects to and "supposedly" will go directly down the wall to the receptable box. This works pretty well on an interior wall with no firebreaks or insulation, but, in my opinion, isn't worth a darn on an exterior wall. The tape trick works well though. I used the heavy duty packing tape.
Hope this helps.