6 rules to actually look good in a suit

Sometimes, it can seem like we at Business Insider are a little obsessive about fit when it comes to suits.
But it really is the most important thing when wearing a suit (besides confidence, but that's more a byproduct than a requirement).
For a suit to look as good as possible, all these different parts of the perfect fit need to come together just so, presented as a cohesive package.
We've decided it's high time to enumerate all these intricacies of fit one by one, as modeled on Eddie Redmayne, the best man wearing suits alive today.
Redmayne has fit down pat, so there's no better teacher.
Let's take it from the top and break it down:
Shoulder alignment.
This is the most important thing you're checking to see if a suit jacket fits correctly. Everything else can be tailored except the shoulders.
 The jacket's shoulder should end before the end of your actual shoulder.
A good way to test this is by leaning against a wall. Ifthe shoulder pad of your jacket hits before your actual shoulder, it's too big. Redmayne's jacket fits well.
High armholes. Armholes are the subtle difference between a well-fitting modern jacket and a poorly fitting, more conservatively cut jacket.
You want them high, but with no restriction of movement. When you move your arm, your whole jacket shouldn't move.
This is another thing can't be tailored, and you must check before purchase. You can tell by the fit of Redmayne's jacket it has high armholes.

Slim fit. The fit of your suit should be close to your body, but not so close that it looks like you're being smothered. A tailor will usually need to take in the sides of your suit to create a trimmer silhouette, as Redmayne has done.
Jacket length. This is one of the easy ones. The bottom of your jacket needs to be long enough to cover your entire butt in the back as well as the entire front fly in the front — and no longer. Some guys with shorter torsos might need to go for short sizes, and they shouldn't feel embarrassed about that — they'll end up looking taller. Redmayne's got it perfect.
Shift cuff and sleeve length. There's no hard-and-fast rule for sleeve length and how much cuff should be showing. A good rule of to have about half of your shirt cuff showing, with your suit sleeve hitting just before your wrist. Short guys should have more cuff showing, like Redmayne has done, while taller guys should have less.
Little or no pant break. Your pant break refers to how much fabric is left over after the leg ends that drapes over the shoes. Right now, fashion favors little to no pant break, and that tends to look the best with the slim fits that are popular now. Our recommendation is a small break, as that tends to walk the best line between trendy and appropriate, as exhibited by Redmayne.