Firstly I have to say these are are good shots of a difficult subject so well done!

Great advice given by Tom & Simon. As Tom says: time, patience and attention to detail  are often the keys to great product shots, with a fair amount of trial and error thrown in too.  I would try bracketing the exposure and getting several shots to blend together this way you can pick the best of each and mask out bits etc.

If done in aperture priority you can vary the light over the objects increasing the dynamic range of what you can shoot.  If you have PS CS2 then this is a perfect subject for HDR images.

If done in shutter priority you can vary the sharpness over different areas therefore choosing your own DOF. This is often done in product shots, just look at some adverts and labels on food you will see the DOF is not a genuine DOF but something chosen by the photographer to emphasise different parts of the image.  It can be very effective if done with subtlety.

Richard.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html