hope this links helps
http://www.photoflexlightingschool.com/Lighting_Lessons/Basic_Lighting/Product___Still_Life/Ring/index.html
- a tripod is a must
- the camera flash is too harsh, try the natural light or other sources;
- you might need a reflector to bounce the light;
- use macro mode of your camera, and crop out the subject;
good luck!