Audiences form an impression of you based on more subtle things than what you say. How you look, your demeanor, how "together" you are all affect what an audience thinks of you...before you even open your mouth.
Malcolm Gladwell in Blink tells us that consumers "transfer sensations or impressions that they have about the packaging of a product to the product itself." I think it's equally true that audiences transfer impressions they have about the presenter of a message to the message itself.
Here are some techniques for packaging yourself to ensure that the transferred impression is positive.
WHAT TO WEAR
Your "costume" speaks volumes about your persona. The care with which you dress yourself for a presentation communicates to your audience your intention and attitude about being there. Do you show up crumpled and creased? Clothes ill-fitting? Shoes scuffed? Needing a haircut? Or are you neat, coordinated, wrinkle-free and well-groomed?
Attire should be appropriate to the occasion. A tuxedo, for example, at an event where the dress is business casual would be pretentious and inappropriate. A good rule of thumb is to dress as well as, or slightly better than, your audience. So at the business casual event, wear a jacket and tie (men) or a jacket and sweater/blouse (women). If your audience is in shirt and tie, wear a suit.
Don't wear anything that will create distraction for either you or your audience. Ditch the jangly bracelets, clothes that you tug and pull on because they don't fit properly, long, clanky necklaces, glasses that you continually play with and uncomfortable shoes.
HOW TOGETHER ARE YOU?
Part of your package is the behaviors the audience sees before you speak. Do you arrive on time or come flying in with seconds to spare? Do you appear well-organized or is a cloud of chaos following you around? Do you appear calm and personable or do you avoid eye contact?
It's a good idea to arrive at the presentation location at least 20-30 minutes before you are speaking, depending on whether you are simply going to another location in your office complex or to an outside venue. This gives you sufficient time to accommodate any unforeseen delays -- traffic, slow cabs or subways, needing to go back to your office because you forgot something, etc. The worst that can happen is that you are early, which then gives you time to take a deep breath and visualize your delivery. It also gives you time to make sure you're organized, have your notes, handouts, glasses and you're actually in the right place.
It's also very useful to spend a few minutes before your presentation starts chatting with a few of the people who will be listening to you. If the set-up doesn't allow you to interact, at least make eye contact and smile. This will start to establish rapport, give your audience the feeling that you are pleasant and approachable and break the ice a bit if you tend to be nervous.
The whole package is what your audience sees and responds to as they determine the value they will place on your words and message. Spend time packaging and presenting yourself, in addition to preparing your content. There is indeed truth in the old proverb, "A picture is worth a thousand words".