If your pictures look fuzzy or blurry, the fuzziness is probably caused by one of the two things.
One is that your camera/hands shook while you were taking the picture. This can be solved by using a tripod or put your camera on an even surface when taking the pictures.
The other problem and also the most common problem is that your pictures are out of focus. To correct this problem, all you have to do is to get focus by turning on the Macro function on your camera!!! It is not really a big trick but only that most people do not aware of this function. Since this is the most common problem people having, let me explain the macro function in more details.
What is Macro?
Macro is generally symbolized with a flower and usually come with almost all digital cameras. When selected it will tell your camera that you want to focus on a subject closer in a short distance but the background is not. Do you remember seeing those extremely close-up pictures of insects or flowers? Those pictures are taken with macro mode is selected.
When macro is selected, a flower icon should appear on the camera screen. Put your camera close to the subject, the minimum distant is vary with different cameras. Then press the shutter button half way down until you hear a beep sound, it will show a small green rectangle on the screen, sometimes it shows more than one. Everything that falls into the rectangle(s) will be focused. Try a few times to have the green rectangle appears on where you wanted to be focused on the picture and when you are ready, press the shutter button all the way down to make the shot. Please note that for most of the digital cameras, if you just press the shutter button fully without pausing halfway, the image will be blurry!!

I found that it is easier to use the Portrait mode, instead of Auto mode, to take most of my jewelry pictures. In Portrait mode, I set the AF Frame on my camera to be in the Center. So, every time I use this mode, a white rectangle will appear in the center of the screen. All I need to do is to turn on the macro function and put the camera close to the subject where I wanted to focus within the white rectangle and shoot!
I encourage you to explore your camera and find which mode you feel more comfortable using. Then, try to shoot a few pictures with the macro function and you will see the pictures are much sharpened. However, to have a sharpened and clearer pictures, proper lighting is equally important!
Proper Lighting
If you picture looks too dark, it is probably not getting enough light.
If your picture looks yellow, it is probably the pictures taken under ordinary household lights.
If there is a harsh white light shown in the picture, it is probably due to the flash from the camera.
Here are some helpful tips:

When shooting indoor, flash will not make your picture brighter but make it worse. So, please have the flash turned off. The picture of the right show the button to turn the flash off on the camera. If you cannot find similar button on yours, you can refer to your users manuel.
To improve lighting, you can
1. provide as much natural lights as possible by opening curtains/blinds or even door.
2. use lamps to add light but make sure it is Daylight bulb, ordinary household light will cast a yellow light and make the picture look yellow.
3. use a light box/photo tent. If you are interested in making an inexpensive light box/photo tent, you can read my other
tutorial. Believe me, it does make a different! However, the pictures showing in my shops were not using a light box/photo tent. I wish I knew that earlier so that I would save a lot of time on editing my pictures. :o)
I am not a pro photographer but I hope you will find these simple tips useful! Showing good quality pictures to your potential customers will increase your chance of having a sale.