A man looks his best when he's wearing a suit. A suit minimizes flaws and maximizes strengths. It makes you look better than anything else you could put on, if you know how to pick a suit that is right for your body shape. The wrong suit will do the opposite of what it's supposed to, and it's not just about the cut. Patterns and colors matter as well. Here is a guide on body shape to help you look your best.
The jacket should be long enough to cover your rear, but only just. Too long and your legs will be unfairly shortened. Get a 2 button with side flaps, pinstripes or solids are okay, make sure the lapels aren't too wide. Avoid anything horizontal--cuffs, wide square patterns in your suit or shirt, and horizontally striped ties. Go fitted anyplace you can--in the shoulders, the jacket waist, and the pants.
The Inverted V
If your largest area is your midsection, go for a 1 or 2 button jacket to elongate your torso. Pinstripes are also helpful. To offset your shape, opt for stronger shoulders and a wider lapel. V neck sweaters can be flattering. Dark solid colors for your suit are best. Like the square shapes, you should avoid horizontal lines. And baggy pants don't solve anything. The extra folds only break up the vertical lines your trying to create, so make them comfortable but as fitted as possible.
Tall and Skinny
You can wear a 3 button or a 2 button jacket, preferably with the buttons set a bit higher up on the 2 button. Brighter/bolder colors in the tie and shirt will draw attention to your upper body and help create breadth, as do square and plaid patterns. Solids are good, stripes only make you look taller and skinnier. Just because your skinny doesn't mean you need extra padding or extra cloth. Keep it fitted so it doesn't look like it's hanging off of you. Your pants should be pleatless. Cuffs are optional.
The Athletic V
If you're muscular, your suit should be fitted (notice the recurring theme? A suit with a nice silhouette is flattering, and doesn't have to be restrictive) but make sure biceps aren't detectable. A 2 button suit with narrower lapels goes with your body shape nicely. You can wear pinstripes, solids, and, depending on how wide you are, square and plaid patterns.