When a man chooses or wears a suit, we usually focus on three main principles.
1. How to button up clothes
According to current international business suit etiquette, when wearing a one-button single-breasted suit, men must unbutton buttons when they sit down. Comfortable; one row of 2 buttons, buttoning top button means solemnity, for taller men, sometimes it is necessary to button bottom button so as not to reveal too much of belt and belt. One row of 3 buttons, buttoning middle button means authenticity, and buttoning top 2 buttons means solemnity. 
Button method for a single-breasted suit
In a double-breasted jacket, you usually need to fasten all buttons, and sometimes bottom button may not be fastened. The design style of a double-breasted suit is somewhat more stable, so method of buttoning should be relatively conservative.
Double-breasted suit button method
Typically, a double-breasted suit has 6 buttons, but only 4 buttonholes, so you should try to button up as many as possible.
Second, how to wear a shirt
Shirts worn on formal occasions should preferably be plain. It is worth noting that long-sleeved shirts are formal wear, while short-sleeved shirts are casual wear, and latter are generally not suitable for pairing with a suit.
Long-sleeve shirts must have a collar, and if a tie is required, top buttons of shirt must be buttoned up.
3. Ties and accessories
Generally speaking, you should wear a tie when you wear a suit. On formal occasions, you should pay attention to color of tie. If you are afraid of making a mistake, it is best to choose one color, which can be same color or color system as suit.
In addition, leather shoes that match costume, as usual, should be dark and solid. Socks should not be too revealing, usually dark socks with dark suits and light socks with light men's suits.
By mastering rules of etiquette and detailed costume instructions, we can look better when we normally wear costumes.