1 - The Shoulders

A good suit starts at the shoulders. It should fit your posture and flatter your frame. If your suit jacket doesn’t make you look better when you put it on, you’re wearing the wrong one.

2 - The Lapel

Avoid narrow and extra wide and keep it somewhere in the middle. Also consider whether you prefer a notched lapel-which is customary-or a more dramatic peaked version.

3 - The Buttons

Suit snobs pay close attention to the buttons on the sleeve of a suit jacket. Most suits, even those from top European designers, have sleeve buttons that don’t actually unbutton but are strictly for show. The best suits have working button holes on the sleeves. And while you’re not likely to ever see anyone rolling up the sleeve of the suit jacket unless his name is Michael Jackson, some flashier types like undoing these buttons in order to show off the superior hand tailoring of their garment.

4 - The Pattern

Stripes and checks are the most popular patterns for suits-though these are often so subtle they are not noticeable from even a short distance. A better suit carefully matches where the patterns meet and overlap, with stripes continuing across the seams perfectly.

5 - The Pockets

Most suits are delivered with the pockets sewn shut. Pull them open but don’t load them with your phone, keys, or iPod as this will ruin the silhouette.

6 - The Lining

Subtle or shocking, a good lining, like functional button holes on the sleeve, allows suit junkies another opportunity to demonstrate their sartorial flair

7 - The Stitching

Superior suits are hand-stitched by a tailor. Although fusing-a fancy word for the suit being glued together-is commonplace for off-the-rack suits, a truly handmade suit will be sewn by artisans. This will be reflected in the price.

http://www.details.com/culture-trends/celebrities/201411/brad-pitt-fury-fashion-shoot?slide=2#/slide=2

  1. Shoulders - The seam should be at the very top of your shoulder, never extending further, as it creates an indent on the arm.
  2. Shirt - The amount of visible shirt at the back of the neck should match the ½ inch of visible shirt sleeve cuff. The collar should be tight enough that two fingers cannot fit between your neck and the shirt.
  3. Jacket - A jacket should hug your body, curving in at the sides. The length should cover your seat and not extend past your knuckles. 
  4. Tie - The tip of the tie should generally fall to the center of the belt buckle.
  5. Pants - Pants should be slim from the waist to the top of your shoes, with a slight break or no break.
  6. Sleeves - Shirt sleeves should stop at the base of the thumb, with the jacket sleeve ½ inch shorter.

http://www.bearingsguide.com/