Before purchasing surge protectors, you should conduct an inventory of your sensitive equipment. This inventory is simply a walk through of your home to determine where and what type of sensitive equipment you have.
Go room by room listing each piece of electrical equipment. Note whether or not the device is connected to the outside world in any other way besides the power line, like telephone lines, modems, or antennas.
You'll also want to note whether items can be grouped to share a multiple outlet device. Then sit down with your list and determine which of the items you want to protect, and make a surge protector shopping list. Pay special attention to the units that will require cable or phone protection in addition to power protection.
Consider only those products that are UL listed as transient voltage surge suppressors, or TVSS. Any number of products will have UL labels listing them as multiple outlet devices. This does not mean the product is a UL listed surge suppressor.
One of the most important performance characteristics of a surge protector is its "clamping voltage". This is the voltage the surge suppressor allows to pass through to your equipment before diverting to ground. The lowest clamping voltage recognized by UL is 330 volts or .33 kilovolts. The product's clamping voltage will be listed on the product next to the UL label if it is UL listed. Select only those plug-in protection devices with a 330 volt clamping voltage. Some manufacturers list very low clamping voltages on their label or in their product literature. View this information for what it really is ... marketing hype. Always use the UL number as your purchasing guide.
Over time all surge suppressors will wear out. Most will provide years of service under normal conditions. However, it's important to know when the product fails. Look for products with indicator lights, audible alarms, or power disconnect as a failure warning. Without one of these you could be unprotected without knowing it.