When checking the system beyond a visual inspection, use a plug-in circuit tester. You can get one at any good home supply company. Get the type that also contains a ground fault circuit tester. They cost about $12.00. The tester has three lights on it, one is red and two are yellow. There is a button on it for testing the ground fault circuits. It also has a small chart on the one side that explains the different combinations of the lights. The second tool you will need is called a voltage sniffer. It looks like a fat ball point pen. It will make a noise or flash a light when it is near a live electrical line. You may have to go to an electrical supply company to get one. The sniffer will run about $25.00.
Take a look at your receptacles. Do they have two slots with a small hole? The small hole should be on the bottom, but about one in ten residential electricians install them that way. Three-hole receptacles are capable of being grounded. If they only contain two slots, you will need an adapter to get the three-prong tester to work. Lets go through testing the three-hole receptacle first. Simply plug the tester into the receptacle. The two yellow lights should light. If anything different happens, you should check the chart on the back of the tester. Now, write down the results, and the location of the receptacle. When you check the receptacles in the bathrooms, garage, exterior, and the receptacles above the counter area in the kitchen, push the test button on the tester. If the receptacle is grounded, the power should cut off. If the receptacle is not grounded, it wont trip or cut off the power. My suggestion is that you get the receptacles grounded. They are safer if they are grounded. If the power doesnt shut off, look in the main panel box and check all the receptacles in the house. If you find a receptacle or breaker with a button on it marked test, push it. Go back and the power should be off at the receptacle. If it hasnt shut off and you have no other receptacles with the test and reset buttons, that receptacle is not on a ground fault circuit interrupter. Get one installed. If the GFCI has tripped reset it with the reset button and continue testing the remaining receptacles in the house. The GFCI will work on an ungrounded outlet. A GFCI can also protect up to five receptacles besides the receptacle where it is installed. A whirlpool should be on its own GFCI.
You want GFCI protection on almost all receptacles near water. This includes bathrooms, above the kitchen counters, on the exterior, and in readily accessible areas in the garage. You should not plug a freezer or refrigerator into a GFCI protected receptacle. People often make this mistake, particularly in garages. The GFCI can trip in high humidity, during a thunderstorm, or from the surge of the motor starting. This can lead to a sad surprise when you get those steaks from the garage freezer. The receptacle for the sump pump should not be on a GFCI either. Although this does involve electricity and water, you dont want it tripping during a thunderstorm when you may need your sump pump. The second result you want is all the remaining receptacles to be properly wired. Improperly wired receptacles can indicate nonprofessional electrical work. Nonprofessional electrical work burns down houses.
The second type of system, found in older homes, is the two-prong or two slot system. Plug the tester into the adapter you purchased. On the adapter is a small round piece of metal that lines up with the screw on the plate covering the receptacle box. Plug in the tester and push the metal against the screw. The ground light or second yellow light should light. If it doesnt light, the receptacle box inside the wall is not grounded. If any other light on the tester lights, the receptacle is improperly wired. I would be more concerned about improper wiring than the lack of a ground wire, however both are important. Write down the location of all the receptacles that did not test properly, and the defects observed on them. GFCIs are a very high priority, and you should have them installed as soon as possible. Remember those hanging wires? Hold the voltage sniffer close to the wires. If they are live, it will go off. Any live uninsulated or improperly protected electrical connections should be corrected immediately. At this point, show everyone in the house where they are so they may avoid them. Someone could be killed if they touch them before they are corrected. Practice using the sniffer on a cord for a lamp so you can see how it works. Next, run the refrigerator, the washer, dryer, and all the ceiling fans. Hold the voltage sniffer next to them. If it goes off, they are not grounded and should be on grounded circuits. Your highest priority is a safe electrical system. First, get the GFCI protection installed, and all live unprotected or unsecured wiring corrected. Next, ground the major appliances, and last, get the branch circuits grounded. Now, call an electrician and recite your "laundry list" to him. Hint: The bigger the job, the faster they seem to respond.