How a Suit Should fit and sit
It's all about the fit. The fit is key and the most important thing when getting measured for a suit.
The shoulders of a jacket should be in line with your shoulders and not hanging over your shoulders. If a suit is too big in the shoulders, the shoulders begin to collapse.
The jacket should fit very closely without being tight to your body and chest to give you a sharp defined polished look. You should be able to fasten up the top button of your jacket without too much pull and without an X appearing on the front of your jacket. Never fasten both buttons on a jacket, fasten the top one never the bottom.
The trouser waistband should be wearable and comfortable to determine the correct size you should be able to insert three fingers in between the waistband of the trousers to dictate that you are in the right trouser size.
The leg length should be long enough with just no brake or one brake of the fabric hitting the bridge of the front of your shoe. To cuff or not to cuff it's up to you.