As you already know, in order to have the right hairstyle you must adapt it to your face shape. If you have a triangle face shape, you will want to try layered hairstyles (soften the jaw line and help you balance) and styles that taper at the jaw line. But you must avoid hairstyles that will draw attention to your jaw line. For example, you should avoid straight solid bob cuts. Anyway, shorter haircuts look better than longer.
A good short layered hairstyle should put the hair exactly where it should be in order to make your triangle face look proportional and balanced. You should use heavy top layers. They will allow for your hair to be fuller and rounder above the ears. In order to make your face look longer don’t use bangs. The most common mistake you can make is to have a bangs that are heavy and falling forward, in the eyes. Because this makes your face look wider and shorter, you must avoid bangs.
A god medium hairstyle should have sides that fall softly away from the jaw line. This should create cover in the right places. Also, side-swept bangs are used to create diagonal direction. You can also use zig zag parts because they will build some length and add some height. The worst hairstyles you can have are those who will make your face look too square or too wide.
If you want a long hair style, you should use soft waves. They have a nice appearance that falls perfectly to the layering. The middle part should be used to create the illusion of length.