Whether you have experienced seemingly overwhelming fear or distracting nerves, your confidence will come from your interest, your preparedness, and your handling of the situation. Confidence will also likely come with time. With time being of the essence, let's tackle what you can impact and own yourself through your DEMEANOR:
D - Decide you believe in you. After all, the audience wants you to succeed, and whoever hired or asked you to speak believes you are a great choice.
E - Eye Contact. Look at the audience. Let the audience know you want to see them. Being connected through your eyes will give you insight (no pun intended), and eventually calm you through that feedback. Stay engaged with one person through a full thought/sentence in order not to look jumpy. Do not look over the crowd, as many early public speaking instructional suggested. People can tell you are not making eye-contact, and either judge you as 1) aloof, or 2) scared...neither of which are good for you! Move on from one person after a thought is completed, so as not to appear you are having a personal conversation, and/or that you are alienating everyone else. Additionally, you want to move on to include everyone in the audience and never give one person the stalker-effect where you keep hanging on them throughout a full segment or talk. Work eye contact in reverse if someone is being disruptive or talking with someone during your presentation. Resist the "dagger eyes", and instead, move close to the disruptive audience member without eye contact or comment...even sit on the table where the person is acting out, and watch/hear how the disturbance will be softened or stifled, without a word or becoming the "school marm" asking for silence.
M - Managing the Room. Talk with others as you check out the space. Walk around during your presentation. Make sure everyone can hear your voice. By stating something like "I take it you are assertive/professional/bold (your choice) enough in the back to let me know if you cannot hear me. I like that about you!" shows that "moxumility"Ô again by showing the moxie to mention it and the humility to offer a solution. It's even better than asking people sitting in the back "Can you hear me in the back?" If you are comfortable with your materials and your projection, you may want to lower the volume to draw people in, and then raise the volume to make key points and show emphasis. As long as you can picture, feel and hear your voice filling the space and the minds of the audience, you can do it!
E - Enthusiasm. Being enthusiastic does not mean you have to be loud; nor does it mean you should be loud. Enthusiasm is a confidence in you and your topic, a respect for yourself and your audience, and an energy that exudes from you that can be read...and even be contagious! A smile and sincerity are your two best assets in showing enthusiasm, and allowing others to appreciate your style.
A - Appreciate your opportunity to speak. Acknowledging your excitement/enthusiasm is not only okay, it is encouraged. Being too laid back can present as cockiness instead of calm. Say something like "Thank you for including me". Be sincerely appreciative of your opportunity. People want others they connect with to do well.
N - Normalize your situation. Eat well, be rested, wear what is appropriate, comfortable, and is true to the audience, activity and you. Have a mantra for your mental calmness. (I use my personal brand sometimes, and other times I simply repeat "You are engaged, you are engaging, they deserve the best you!") Whatever you connect with that is a fit for repeating internally that is positive and focused, is a healthy mantra for you.
O - Offer intonation in your voice and movement in your presentation. Pace and tone changes that are not too wishy-washy or high pitched both offer variety, and therefore keep people's attention.
R - Relax yourself naturally. Meet a lot of people prior to going into the room or up on stage. Be "that person" who is welcoming, friendly, and approachable. Breathe deeply before going "on". Keep breathing intentionally and deeply (watch the noise if you have a lavaliere microphone!!) to keep your voice and pace in control. Have room temperature water close at hand, and ensure you hit the restroom before your presentation (one, to go to the bathroom, and two, to check your appearance).
Your DEMEANOR is your style. Let your demeanor convey your nerves as confidence, and your eagerness as energy, and let your passion for your presentation wow the audience in a way that is respectful, rewarding, and warrants a terrific response!