a $3 tester has two probes and a small neon light i bought last week
from walmart superstore electrical dept.
read all of this first: with your friend the licensed electrician who
knows cpr standing next to you: with one hand in your pocket, you can
carefully chase the circuit thru switches with one probe grounded and
the other probe touching the wire resulting in a glow. the electrician
will show you how hot 110vac to one probe glows when you touch the
other probe.

see pictures of testers at:
http://images.google.com/images?sour...neon+tester+ac