While plug-in surge filters and UPS devices are valuable, I also recommend (as another stated above) a unit mounted directly on your mains panel. This you can't buy at your average hardware store, in fact can't say where you'd find one except at a electrical wholesaler or specialty suppliers, such as a solar power dealer. These are attached directly to your breaker panel with the usual threaded mounting into a side knock-out, and occupy two circuits on the panel. This offers a greater level of protection, and believe me, if lightning strikes, it goes pop and saves stuff down-line. This I know for a fact! A $100 pop saved maybe $8000 of stuff in my house.
Another challenge for our circuits is low or high voltage coming down the line. Don't believe that your power is always a nice and clean pure wave, locked in at the proscribed voltage. It does vary somewhat. You should put a meter on the line voltage to see what you've got.
Doug
in rural Ontario