I get questions about shooting jewelry all the time. Luckily I am a professional photographer as well as a jewelry designer. It's actually much easier than you might think! No need for fancy equipment, except maybe a nice camera but honestly you can shoot with your cell phone if you absolutely must.
1. Set up. Find a spot next to a window with nice light. I did not shoot these on a sunny day but a typical overcast gray Michigan January day, which is perfect. If it is bright and sunny do not shoot jewelry directly in it. You can tape a "filter" on the window. Use a piece of translucent paper if you have it or you could use a thin white sheet or even a thin white button down shirt. What you are looking for is anything that diffuses the light so you don't have harsh shadows. For these shots I used a wood bin I got at Home Goods and turned it upside down. I have a marble top table in my studio that I used for some of them and then when I wanted a crisp white background I just used my sketchbook. I liked leaving the sides of the notebook showing to create some interest. I used a fake plant I have around for my art fairs.
2. Bounce that light. Get a small piece of white foam board. You can get them at any office supply store or sometimes dollar stores and drug stores have them too. You are going to set it up (or hold it like I do) on the opposite side of the window to bounce the natural light on the side of your jewelry that isn't getting the light.
3. Tripod. This is important if you are using a SLR camera because taking a nice slow exposure can do wonders. However, my Canon Mark III does a fairly good job with handheld at a slow speed so with these photos I just held my camera. Plus I was in a hurry and shot these really fast.
4. Extra light. Now here is the tricky part. In my studio I have really nice fluorescent lights that just happen to be daylight balanced. When I'm shooting portraits I turn them off and rely on strobes but when shooting jewelry I leave them on. They are pretty perfect. If you have to add lights, stay away from yellow based lights and try to shoot it with only natural if you can get away with it.
5. Exposures. I shot these with my ISO at 200, f4 and 1/20 sec. I used my wide angle (by accident actually because I grabbed the wrong lens but it worked out great) 16-35mm. Yes, these are handheld at 1/20th. Crystal clear too.
6. Editing. I use Lightroom and I love it because I can edit many images quickly. It also has a way to compensate for the lens you are using and with a wide angle this is important because it gets rid of the curved edges and pops it out. For these I did a very simple setting. Exposure +.50, white balance is set to "as shot" which was neutral in my camera and the lens was set. For the dark background ones I added a vignette to it. For some of them I did some spot adjustments by lightening up the amethyst and increasing the saturation slightly. When selling jewelry online you want to have clear and concise photos without too much photoshopping because you don't want your customer to be disappointed when they receive it.
7. Tagging. This is important. If you are using lightroom you can add keywords to your images when you import them. Use words that people would use to search for your item. For example, jewelry, necklace, handmade, one of a kind, artisan, etc.
8. Cell Phone photography. Of course, having a fancy camera makes these images look professional. But you can get away with a cell phone sometimes. A basic thing that a lot of people forget to do is to clean your lens on your phone. It makes a huge difference! Hold your camera very still and zoom in slightly but not too much or you will get a lot of grain. You can use the editing in the phone but I like snapseed for editing. There is a filter called "drama" that you can really lighten a shot up with. Just remember not to overdo it with the filters or the photos will be begin to look fake and that is a turn off to potential buyers.
That's it. I seriously took these photos in less than 20 minutes and spent about another 20 minutes editing them. The main thing is to play around a bit. Shooting in RAW if you can is the best because you can really adjust everything in lightroom.