Naturally you'll want to take time to groom well for any presentation appearance. Unless you're Albert Einstein, uncombed hair and disheveled clothing will make an audience perceive that you didn't care enough to clean up for them.

How you dress also counts. Whenever possible, dress like your audience, or a 1/2 notch up, while wearing clothing that is comfortable and allows you to feel your most confident.

Why?

This will set your audience at ease and set an "I'm-one-of-you" tone. We live in the age of business casual, so if your audience will be in polo shirts and khaki pants, they'll feel more comfortable if you are too. If you don't know what your audience will be wearing, the general rule is to dress up a little. You can always remove a suit jacket or blazer to become less formal, but it's hard to turn jeans and a sweatshirt into business wear.

How?

Press your clothes whenever possible -- even casual clothes. When packing your clothes, put them inside plastic cleaners or garbage bags before you load them into your suitcase. This captures air and you will end up with fewer wrinkles. This gives an impression of crispness and neatness. 

If you're wearing a suit or blazer, keep the jacket buttoned until you're ready to make a "let's roll our sleeves up and get to it" impression. 

Different colors mean different things. Loud colors can seem confident but can also seem aggressive. Darker colors can appear subdued but also dull. Know what works for you. 

Hair, watch and shoes are big indicators that can either align you with your group or alienate you from them. A few, common sense tips: 

Men - a zippy New York haircut doesn't play well in rural areas, but a furry neck doesn't win anywhere. Women - sharp updated and often trimmed hair sends a very positive message. 

Leave the flashy jewelry in the drawer. Diamond pinky rings or lots of jewelry play only to selected audiences. 

Logo attire can be risky. If you're going to wear THE client shirt, make sure you have the current version. If you're at an event with multiple clients, wear something plain. 

Shined shoes in good condition go well EVERYWHERE! And make sure that soles of your shoes are in good condition. 

Belts - leather should match - brown with brown and black with black, etc.

The suggestions above apply pretty much equally to men and women. However, women often have extra hurdles in terms assuring that hair and make-up, as well as attire, are aligned correctly with the audience.

Benefits:

* To be more confident wearing what makes you feel confident and knowing you are at your best. 
* To make the audience comfortable and demonstrate alignment with their environment, simply to "be one of the group". 
* To open the audience up to what you have to say, not what you look like. 
* To demonstrate strength.

Action Plan:

When you, or your staff, plan your next presentation, audit your wardrobe and grooming in advance. Select someone on your staff who is "really picky" to do the audit, and equip him or her with a profile of the audience and the context of your session.