Artist trying to be a better photographer

This sounds strange, but its true. I am not content with my art photographs. I have Nikon D40 SLR camera which is supposed to be pretty good. I use a 50 mm lens for taking my photos. The photos are not as sharp as I would like.
I got some tips from today.
  1. Use only one type of light source
  2. Set the white balance
  3. Set zoom to middle range
  4. Fill the viewfinder with the whole image
  5. Use self-timer, even if you are not using the tripod
  6. Focus, focus and focus
  7. After taking the image, zoom it in the LCD and look at it closely