If you want people to fear you by means of intimidation, then I could tell you how. The best kind of intimidation is the one that is implied. When you point a gun, you want people to fear the one welding it and not the gun. Scaring someone is not intimidation. It's about getting that respect for your power and authority.
Looks can be one of the easier ways to do so. Be mysterious and impossible to read. Not shaving or a trench coat will do the same thing as a clean shaven look with a suit. This is up to you, but you want people to know less about you. The more things left to their imagination, the more menacing you are to the opponent as they try to fill the blanks. People fear the uncertainty and unknown. If you don’t want to be the “crazy, unbalanced” type, then you can make people fear you by just being silent and composed. Never say too much of anything. Never flinch to anything the opposition says. You want to speak in a direct, snappy sort of way, the kind that channel that you mean business. No smiles, no blinks, just straight to the point.
Oh, and size do help. If you can’t be smart with your words and composure, then work hard hitting the gym.