Tucking your T-shirts into your pants or sweatpants won’t make you look ’’cool.” In fact, it will do just the contrary since it will make you look like a middle-aged man. Leave your T-shirt un-tucked as tucking it in will crinkle it up, giving you unwanted lines on your body. If you’re wearing sweatpants, the un-tucked T-shirt will cover the drawstrings and you’ll look tidier — not like you’ve just rolled out of bed. Of course, there’s an exception to every rule and for this one, it’s tucking in the undershirt one wears with a dress shirt.