This casual pairing of a white and black plaid flannel long sleeve shirt and black skinny jeans is a real life saver when you need to look great in a flash. A pair of white leather low top sneakers will put a dressier spin on your outfit. So if you're searching for a look that's sharp but also entirely spring-friendly, this just might be it. And if we're talking casual fashion tips for 20-year-olds, this combination looks great on most men.