1) Make sure you choose the proper sleeve length, which means the cuff should land on the mouse of the hand.
2) Cuffs should be quite narrow around the wrist, just a little wider on the side where you wear your watch.
3) Comfortable but not too wide on the neck, or the tie won’t ‘sit’ properly.

4) High in the armpits, tight around the shoulders. 

5) Sleeve length of the suit should be about 2,5 centimetres shorter than the shirt sleeve for the right look. If longer, your appearance will instantly become shabby.

6) High in the armpits, natural fits on shoulders to follow the shirt.

7) A sleek fit on the body is essential; make sure the jacket can just about close.

8) No pleats on the front of pants, they make it wide and old-fashioned. Go for narrow, but make sure you can still sit down comfortably. 

9) Pants should land right on the shoe or just above, no folds, it will make you look smaller and older, and definitely not slim or stylish.

10) Buy a high-quality brand and fit, it’s the first people will look at and it’s all about comfort.

full list via  antihelden