Wearing a suit is armor of modern gentleman, as well as a manifestation of masculine taste and style. Different people, different scenes and different uses have different ways of wearing formal wear.
Fitness is definitely key to wearing a suit. Whether you make clothes to order or buy ready-made clothes, you need to consider following points:
Shoulders. The shoulders of blazer should remain smooth where arms naturally hang down.
Pants Length: Some people like to cover their toes and others like cropped pants to show off their ankles, it's a matter of personal preference. But generally speaking, cuffs of your trousers should fit snugly against your shoes, not be too long or wrinkled.
Sleeve length: The cuffs of shirt should exceed length of jacket by 1-2 cm, in order to better change proportions of human body.
In addition, we need to understand:
What costume should we wear for what occasion.
One piece suit - even refers to jacket, which is not paired with trousers and is only suitable for informal occasions. For example, in fashion industry, new media, or companies that don't have a dress code, this can be used as casual wear.
A two-piece suit is a set of a jacket and trousers made of same fabric, color and style, as well as styles that overlap with each other. If you're going to an interview or meeting with a client, it's a good idea to make it a bit more formal.
Three-piece suit: top, pants and vest. A three-piece suit is more formal than a two-piece suit. Therefore, when participating in high-level business events, you can wear it like this. Such as high class forums, award presentations, meetings with dignitaries, etc.