Once you've removed a cover plate or light fixture, it takes only a few seconds to check the wiring inside for damage or unsafe connections.
Shut off power and test to see that power is off before you touch any wires. Use rubber-grip tools. Often you need to gently pull the device out of the box to inspect it.
Always assume that the wires are hot, even though you have de-energized the circuit. Touch only wire nuts or wire insulation -- never bare wires.
Before you replace the devices in their boxes, wrap the terminal connections with electrical tape if local codes allow. The added protection helps hold wires in place and keeps terminal screws from touching the sides of a metal box.
The black or colored (not green) wire (hot) must be connected to a terminal with a brass-color screw; the white wire (neutral) to the terminal with the silver screw. If the wires are reversed, the receptacle supplies power but is not polarized. Connect the wires to the correct terminals.