A few tips you can use as a home owner to check your system (or system components). You will find the presence and/or condition of these items on my inspection report. Here goes:

PLUMBING: The T&P valve is an important protective device for your gas-powered water heater. T&P stands for "temperature" and "pressure". If temperature and/or pressure reaches a critical level the T&P valve kicks in and releases water to a line that is connected to the valve.

How to test it: NOTE: LIFTING THE RELEASE LEAVER IN THE RELEASE POSITION MIGHT CAUSE THE VALVE TO LEAK. Instead,tip the lever slighty in counter clock wise or clock wise position. If the lever does not move, it is time to consult with your trusted plumber to replace the valve.

Other source: This YouTube video clip:  http://www.youtube.com/watch?v=rleeW2AcRKU

KITCHEN APPLIANCES: The one major kitchen applicance mostlikely not properly installed is the cooking range. Not properly installed refers to the fact the range is not secured to the floor or wall (varies by model) to avoid tipping. 

The range should not be able to lift in the back and as such prevents the slipping of cooking ware off the burners.

How to test it: NOTE: TURN ALL RANGE BURNERS OFF AND REMOVE COOKING WARE. TURN OFF POWER/FUEL SUPPLY. Simply hold the range on the top and try to pull forward.

Other source: http://www.youtube.com/watch?v=fXWl0Iuw5XE

ELECTRICAL: Test your GFCI outlets. GFCI stands for "Ground Fault Circuit Interrupter" and as such provides protection against a grounding fault, which is the most common form of electrical shock hazard. A grounding fault occurs when a "hot" wire comes into contact with a grounded enclosure. If a user operatres a tool or appliance when a ground fault occurs, the GFCI outlets disconnects the power supply.

GFCI outlets are required on kitchen counters, kitchen islands, garage, exterior outlets and bathrooms.

How to test: NOTE: THE ONLY APPROVED TESTING METHOD IS THE TEST BUTTON AT THE GFCI DEVICE, however in the practical world a GFCI tester will be helpful to determine if a GFCI outlet works. 

It is common practice to use "normal" outlets in a GFCI circuit and they are protected as well, as long as the first outlet in the circuit is the actual GFCI device. 

Lets use the bathroom outlets as an example, locate the GFCI outlet - usually only one that protects ALL bathroom outlets - and test by pressing the "TEST" button. With an audible "CLICK" the "RESET" button should release. Power to all connected outlets is cut.

Simply press the "RESET" button to activate the outlet again. Moving on to another bathroom, insert the tester into an outlet and the if the outlet is connected properly the tester will display accordingly. By pressing the button on the top of the the tester the GFCI (in the bathroom it is installed in) should cut the power.

In this manner you can test all GFCI outlets.

Should the GFCI outlet not respond as described, it is time to consult with a qualified professional to remedy the situation.

Other source: http://www.youtube.com/watch?v=1gprgYtQipo