Crystal and other clear or transparent glassware is another difficult subject, but that's because many people treat it as if it were opaque. However, the reason such an item can look so beautiful is because of its delicate transparency.
If you blast away with a camera-mounted flash or place all your lighting in front, near the camera, you will get lots of reflections, not the refraction of light through the glass subject.
You also don't want to use a light tent when photographing glass. That will give you distracting reflections from every surface of the glass, instead of showcasing the transparency.
Rear Window Photographic Lighting
The best approach is to light your glass items from the rear or from the top. You can use either a light or dark background, depending on the color and other characteristics of the crystal. Colorless or cut glass often looks good against a dark background.
So, with that in mind, here's a simple setup for glass, using just a sheet of black posterboard, curved up in front of a bright, non-sunny window, with the light striking a crystal vase from the rear...
And this is the resulting shot...
Shooting Glassware with Artificial Light
That wasn't bad, but I prefer the control I can get from artificial lights in an indoor setup. Here is just such an arrangement, using a single light in a small photographic reflector...
In this case, I've aimed the photo light so it shines almost exclusively on a white paper background, which sweeps up behind the decanter I'm shooting. The decanter is then mainly seen by the light reflected from the background.
Because my background is white this time, I also propped up two small black sheets of posterboard on either side of the decanter. These will be reflected by the side areas of the item and will give it more dimension and shape.
Here's the final result...