Taking photos of art and products is something I personally struggle with, so much so that the first stencil festival I applied to I didn't get into. A few years after applying I gave one of the paintings to one of the selectors as a gift. They told me it was good, I told them they had knocked it back, with which they replied to with 'You should of taken a better photo'.
I recently came across some useful posts on the Making It Lovely website that are full of handy hints and tips:
• Product Photography Part 1
• Product Photography Part 2