OK I worked at Dillard's in the Men's Department. These are my tips because men of all ages would come in there without their mothers/girlfriends/wives to help and had no clue.

1. Make sure the pants are not too long or too short. There is to be one break on the front part of the shoe. Don't let the back of the pants drag the floor but it should cover most of the back of the shoe.

2. "Hug yourself." This makes sure the jacket doesn't stretch too tightly across the back and that it's comfortable.

3. The arm length should only show a quarter of the shirt sleeve when your arms are hanging or relaxed.

4. If getting dress socks, make sure the socks match the suit. For example, get navy socks to go with a navy suit and that the socks are exactly the same color of navy. Gray socks = gray suit. Black socks = black suit. etc.

5. The tie should come down not much past the belt width, if at all. Ties that are too short come above the belt/waistline. The tie is too long if it's coming all the way down to your crotch while standing.