According to Body Type
The rules for choosing boy belts according to body size are simple. If you have a short waist, you will look great with a thin narrow belt that doesn’t overpower your midsection. If you’re long-waisted, get a wider belt to add length to your legs. If you’re not that blessed in terms of height, don’t wear a belt that’s wider than three inches to keep you from looking stout. If you’re heavy, choose a belt that’s simple and in a similar shade as the rest of your outfit to make you look like one long, lean figure and create the illusion of a slimmer body.
According to the Outfit as a Whole
Generally, a leather belt should go with leather shoes, and must be in the same color or, at least, in close shades. The material and design also matter. For example, suede or braided should go with a more casual outfit, as opposed to plain leather, which is usually for formal wear. Even boys can wear striking colors such as green or red, but the belt must come as just one flash of color that adds flavor to an otherwise drab get-up. Sometimes, you can just experiment, trying on different boy belts with different outfits to see which look good with which.
According to the Buckle
Belts won’t be belts unless they have buckles. At least, if you are talking about boy belts. When choosing the right belt based on the buckle, remember that it’s largely going to be a matter of body type. The more robust you are, the larger the buckle you will want. Wearing the wrong buckle size can make you look out of proportion, so do pay attention to this issue. Of course, even the most fabulous buckle becomes useless if it doesn’t keep the belt fastened and your pants up. Third, make sure your buckle is adjustable. You will never know when your waist gets wider.