You'll probably do well to invest a few bucks in an antistatic wrist strap, to keep static electricity buildup from frying your PC's innards. Using lint-free wipes and isopropyl alcohol on the contacts and the insides of the slots should do the trick, but a lot of people prefer to use contact cleaner. When you reinsert the cards, make sure you don't overtighten the screws attaching the cards to the case, as this can partially unseat the cards. Clean the keyboard by turning it upside down and blowing the dust out from between the keys with canned air. Then they aren't made to come off, so quit yanking on 'em.
Power surges cause lots of trouble.
If it looks like an electrical storm brewing outside, shut the computer down and unplug both it and the surge protector. Also, keep the surge protector away from your feet, as it's easy to hit the off switch with a stray foot. Replace yours every 12-18 months. Modem phone lines need protection too. Ancient wiring, glitchy transformers, etc.