Testing for power is not a difficult task, and you don't need to be a pro to do it correctly and safely. Before you do, however, you should watch this video where electrician Joseph Fratello describes the different testers available and how and when to use them. And, as Joe stresses in his demonstration, if you use a non-contact tester—also called a pen tester—you'll want to verify with a contact tester that the power is indeed off before doing any electrical work.
To learn more about electrical testers, read Clifford A. Popejoy's Make Sure the Power Is Off from Fine Homebuilding issue #196 (June/July 2008), pp. 74-77.