Instructions
Decide whether you want a single ocular or a binocular eye glass magnifier. Seeing three dimensional items, such as cut gems, might benefit from a binocular view, while a single ocular is less obtrusive to your view and is better for multi-tasking.
Choose a magnification that works best for your application. You'll easily find powers between 1.5 times and 2.5 times magnification for binocular magnifiers, and single ocular loupes with magnifications ranging from 4 times to 7 times.
Check consumer ratings on eye glass magnifiers on sites like nextag.com. Here you'll also get a general idea of prices and the different types of magnifiers available.
Select a style of magnifier that suits your needs. If you want one that is easily removable, you might want to choose a clip-on style, while if you work on detailed projects all day long, you should select a singular ocular that directly mounts to your eyeglass frames.
Try it out. Before you buy something as personal as an eye glass magnifier, go to a store and try a few styles out to see which one is the best fit.