Dress the part. You can sport any fashion you want off stage and dress to suite whatever company you are in. But on stage you need to dress the part. If you are a banker, dress like a banker. If you are a developer, dress like a developer. Dress for your role not your audience. If you are a banker addressing an audience of developers, dress like banker not a developer.
Dress to the occasion but generally dress one notch up, not down. It is better to be a little overdressed than underdressed.
Quality not quantity. Fewer moving parts is better, each of the highest quality you can afford. I.e. wearing a dress shirt or blouse with slacks, both of high quality, is better than wearing a cheap suit with suspenders and chunky cufflinks. Newer and less worn is better.
Choose clothes that are comfortable to move in. Shoes should be low heeled, with soft soles.
Avoid accessories (jewelry, ties, scarfs) that swing freely.
If you are wearing a suit jacket and the room is warm, do not be afraid to take it off after you are introduced and greet the audience. This is akin to the boxer removing his or her robe upon entering the ring. The presentation is going to be physical and you are getting down to business.