Preventing Electrical Shocks

According to about.com these are the most sensible ways to prevent shock:

1. Be Safety Conscious
Working with electrical circuits can be dangerous if you don’t take certain safety precautions. Electrical shock can not only injure you but also kill you. Practice safety when working on any circuit and slow down! When you hurry through a project, there is a greater chance for an accident to occur.
2. Shut the Power Off
Always shut off the power to a circuit or device that you will be working on. This is the first thing you should do before working on any electrical circuit. I don’t know anyone who has been shocked by a circuit that is not energized.
3. Test the Circuit
After turning a circuit off, it's a good idea to check it with a tester to be sure that, indeed, it is off. Never assume that the circuit is off!
4. Ladders
Ladders are necessary to accomplish some electrical jobs. Never use an aluminum ladder on any electrical project. Always use an insulated fiberglass ladder to keep you safe.
5. Wet Locations
Avoid wet areas when working with or on anything electrical. If there is a reason that you have to be in that situation, wear rubber boots and gloves to lesson your chance of getting shocked. Tools and appliances should be plugged into a GFCI outlet or GFCI extension cord.
Don't forget to dry your hands before grabbing any cord to plug it in or unplug it. Wet hands and a frayed cord don't mix. You reach down to grab the cord and just like that, you've been shocked! Believe it or not, it happens.
6. Warning Labels
Finally, if you are working on the service panel or a circuit, be sure to place a warning label on the face of the panel. This will warn someone not to turn on the circuit that you are working on. There’s nothing worse than turning off the power, checking that it’s off and starting to work on the circuit, only to have someone come behind you and turn the circuit back on. Always think and ask questions before turning on a breaker that is shut off. Maybe someone is working on the other end.

Source: http://electrical.about.com/od/electricalsafety/tp/sixwaystopreventshock.htm