I know what you are thinking - give me a break - I know how to format a flash card. Well, give the article a read anyway. The advise given here is not something I do as a matter of course - that is, format your card in the camera before you start shooting with it. I just sometimes forget, but I'm glad to hear the advice again - I hope to change my ways - New Years resolution #87.
Also, don't delete images from the card in the camera - I've heard that can lead to some "nasties" too. Hey, for a more thorough discussion, I would check out the article right here.