Originally posted by sterretje At the moment that you notice problems that might relate to the memory card, stop using it and use your spare card.
By taking new pictures, data might be overwritten making it far more difficult for recovery software to recover.
It would also seem like a good idea to put the write protect tab to the read-only position until contents are copied/recovered/deemed lost to avoid doing this by accident. After this it would be a good to test the card before using it again for anything critical. If it is to be used in the camera it should be formatted in the camera to avoid trouble down the line.
Actually, I'm in the habit of formatting a card instead of a "delete all" e.g. after coping the contents to the computer. This makes sure the camera gets to use a mint file system matching its idea of a proper FAT implementation.