1.) Build it better.
-- If you’re on the scrawny side, then the mission for you is to help create the illusion of weight, not a lot of it of course, but just a bit more than you have now. If you’re opting out of the high-fashion, ultra skinny look, then easiest way to add carefully controlled bulk is by choosing weightier fabrics, like tweeds and heavier weight wools. Look for cuts that are a bit loose as long but be absolutely sure they are well-tailored so you’re not swimming in extra fabric. Adding a vest as another layer will also help create a bit more flattering bulk.
2.) Step away from the vertical stripes.
-- Vertical stripes will help create a longer leaner look, which most thin guys don’t need. Instead, go for tweeds, twills, small scale plaids, or any fabric that add some texture and visual distraction/interest to the mix.
3.) Hey! Nice pecs!
-- To make the chest look a little broader in the short term, a double breasted jacket makes a good quick fix. For the longer term, may we suggest a few push-ups?
4.) Cuff me, please.
-- To beef up the look of the leg, cuffs can add balance and a thicker line to the lower half, while minimizing the dreaded legs-like-toothpicks look.
5.) Does this shirt make my head look big?
-- When it comes to dress shirts, thin guys need to pay attention to the style of collar on the shirts or risk looking like a bobble-head doll. In general, the classic spread collar is a good choice to help balance out and broaden a thin face. Another style with a slight widening effect is the tab collar, which can also help camouflage a long, thin neck.