My camera takes its fair share of abuse, but my memory cards are treated with the highest regard.  Well, except for the time I ran an Ultra II through both the wash AND dry cycles; that minor incident aside, you can show your cards a little R.E.S.P.E.C.T. by practicing a few simple habits:

1. Format brand new cards in your camera before their first use.
2. Handle cards by the edges; avoid touching the contact points. 
3. Store your cards in their little plastic cases.  Keeps them dust free.  Keeps the lint from your pocket out of the contact points.  I've been seen carrying cards in sandwich bags on many occassions.
4. Reformat your cards often.  EVERY time you put it into your camera is not a bad habit.  This deletes the photos, file names and any miscellaneous data from the card so that left-over data won't corrupt your new work.    Using the delete button in your camera or deleting files via the computer is not  the same as reformatting in your camera.  Leftover data may corrupt your new work. 
5. Never bend or force a card into the slot. 
6. If the memory card is close to being full, STOP shooting; don't risk losing any data when you run out of room.
7. Always turn the camera off before inserting or removing the card, but
8. Make sure the buffer is empty before turning the camera off... did you just shoot in burst mode?  Are photos still being written to your card?
9. Magnets: no, no, no.
10. Don't forget the card in your computer; remove it immediately after backing it up.  The computer will keep accessing the data on the card, prematurely wearing it out.
11. Keep your camera up to date with the most recent firmware.
12. Make sure the battery in your camera is full.  You don't want it to fail while it is writing an important shot to the card.
13. Transfer before you edit.  Editing directly from the card will reduce its life expectancy.
14. Avoid water and humidity (or so they say).  The aforementioned adventure in a jeans pocket through a full wash cycle and a tumble in a hot dryer proved to be no big deal for one of my Sandisk Ultra II's .  It was in its plastic case, somewhat protected, but there were drops of water inside - even the dry cycle did not destroy the card or the data.  Perhaps the "Tide" helped, the card performs just fine and I've actually heard many similar stories.
15. SanDisk's standard flash cards are designed to withstand temperatures up to about 140 F (60 C), and the Extreme III's are supposed to function in any environment that a human can.  But, why not show a little R.E.S.P.E.C.T. and keep your cards at room temperature, not on the dash of your car.
16. Normal airport X-ray machines and metal detectors do not harm full or empty cards, although SanDisk does recommend that you take the card out of your camera before passing through these devices.
17. Did you delete a photo or reformat a card without backing it up?  Don't take any more frames.  Visit SanDisk.com and try out their recovery software.  But if you've already written over the lost file, you are S.O.L.
18. Purchase the real thing.  If you see a price on eBay that seems too good to be true, you are more than likely purchasing a counterfeit card.  The card may or may not work, or it may work, but writing speed is painfully slow.  If it is a real brand name from a unauthorized dealer (gray market) you will have no warranty.  Real cards from authorized dealers are so affordable these days, why take the risk?

Can you tell that I prefer SanDisk?  I've had just one corrupt photo that came from an Extreme III - and I think that the photo was actually fine, but... duh, I was editing straight from the card at the time so we'll never know.  I've heard good things about Lexar, but never used them.  I've heard not so good things about many economy brands.  For me I need a card that will write fairly fast.  I switch between Extreme's for action and Ultras for affordability.  They both actually write faster than my speedlights recycle for posed team photos and that keeps me sane.