A question I am often asked when I am coaching a presenter, is what do I wear?
A simple guideline to follow is to wear clothing that is slightly more formal than what your audience will be wearing. Finding out what your audience will be wearing is part of your research and planning. It is not difficult to work out.
If you are presenting to a TED like audience on a weekend, then you can be sure that your audience will be wearing casual clothing. Therefore it would be a mistake to wear a formal business suit with a tie and all the trimmings. A better clothing combination would be a pair of trousers, a sports jacket or blazer and a buttoned shirt. whether you wear the jacket or not will depend on the temperature in the room. Feeling comfortable when you present in the priority here.
On the other hand if you were presenting the financial performance of your company at your shareholders annual general meeting, then a formal business suit would be the right choice. Preferably dark in colour with a white shirt, black shoes and a tie.
If you were asked to present at a company retreat or workshop, then a more casual approach should be taken. Wearing the type of clothing you would wear for a TED like presentation would be appropriate.
It is also worth bearing in mind any cultural differences. In many parts of Western US, informality in clothing style is normal, whereas in many parts of Asia, such as Japan and Korea, business attire is still largely formal (although I do accept this is beginning to change) Finding these things out should all be part of your research when you are preparing to do a presentation.
The key thing to remember when you are presenting is that the clothes you are wearing should not detract from the main message of your presentation. So, leave the bright yellow socks at home, and wear something that does not stand out. Always keep in mind that you are not presenting to promote yourself, you are presenting for your audience and they really do not want to be distracted by your fashion statement no matter how good or bad it is.