Every man should own at least one suit, preferably two.
First off, when suit shopping, never go alone. The people that work in stores want sell. Bring a trusted friend to warn of bad advice when buying from an over eager salesperson.
When buying a suit, start with the jacket. The first thing to look at is, do the shoulders fit? The sleeves can be taken in or out, the width can even be altered, to a point. The shoulders are fixed. If they do not fit, there is not point in seeing if the jacket needs further alterations.
Next is length. If one has to button the bottom button to make the jacket fall or sit correctly, it does not fit. A suit jacket should fall in a manner that covers a man’s zipper in the front and his bottom in the back.
The slits in the back of the suit jacket are called “vents.” Only buy a vent-less jacket if for standing only occasions, as sitting will wrinkle the jacket. One vent is standard. Some call it the “American” jacket style. This is fine for a dinner jacket – a jacket that is not necessarily part of a suit, for less formal situations.Two vents is the best way to go – especially in a suit – as it makes for more flexibility and ease of movement. A man’s back pockets are more accessible and he simply looks sharper.
While it is not a rule, I recommend one never buy a jacket with only one button, unless it is black and will be used for black tie events. Only taller gentlemen should buy a jacket with four buttons. The safest are two or three button suits as they are always in style.
Once the jacket has been altered to fit perfectly, a man should be able to slip his hand into the jacket, buttoned, and it should fit snuggle, but not tightly, on the chest. There should be room to move. Also, be sure to button the jacket (correctly) while stand up and unbutton it while siting down. Sitting with the jacket buttoned can ruin the suit. Never button the bottom button on a suit or a vest.
When it comes to color, save that black suit for funerals. Charcoal is really as dark as one should go.
Final thought:
As stated before, every man should have at least one good suit. A $100 off the rack suit will fit as well as a $2000 off the rack suit. Have your suit custom/tailor made. It will be worth it.