If you don't want to work in RAW -- too slow or other reason, I suggest you shoot in the FINE (largest) JPG setting. When done, back up your JPG files to a CD or DVD so you always have the original, then convert the JPG to TIFF. You will end up with a that is approx. 18MEGs in size. Do all of your corrections here (never on the JPG) and when you are satisfied with the final product, THEN you should resize to the desired size and FINALLY, convert back to JPG if necessary.
Keep in mind that for best quality, your final image should be 300dpi for photos to be printed, while those intended to be viewed on a monitor are fine at 100dpi or less.
This work flow always leaves you with a backup in case something happens and your final product doesn't suffer from repeatedly resaving a JPG image.