You need to have a voltage tester of some type for electrical work, and one that you trust is working properly!  This can be anything from a $2 neon voltage check, to a $2000 digital multi-meter, or anything in between.  The important thing is to ensure that it is working so you can verify that you have the power off on any circuit you may be working with.  Check it on a known live source before trusting it to determine if your circuit is dead.Your personal safety should be the most important consideration.

  Goggles and safety glasses, gloves, long-sleeve shirts, long pants or bluejeans, hard hat, etc.  A large dose of common sense is required here.  Think about the hazards and protect yourself accordingly before taking on any task.