As a man in today's world we often have to fight for what we want. If we want a woman we cannot be a wimp. Looking intimidating to other men means hands off.
How to Look Intimidating
The first thing you need to do if you want to look intimidating is to get bigger. No not get fatter. Hit the gym and start working out. Hit the weights hard to put on some mass and bulk.
Now you just have to revamp your wardrobe. Get fitted shirts that show off your new found muscle and mass.
If you are willing to I would advise shaving your head. Think of people with shaved heads, they are usually seen as intimidating. I have also found that shaving your head makes the rest of your body look bigger as it draws attention to your muscles and arms.
When you are out in public keep your head up, don't look at the ground, don't smile and look people directly in the eyes when you talk to them.
When you meet people talk in a serious tone, give them a firm handshake and don't let your voice waiver or show that you are indecisive at all. Talk with purpose, project that you are a strong person and know exactly what you want.
Attitude is everything. Act as if you are tough and intimidating and you will be just that.
Don't stare at people in the eyes to long as this may be a signal of a confrontation.