You’ve crafted the message and created the slides for your next presentation. Now it’s time to wow the audience. How you look and sound are going to make a big impression — and your audience will form opinions quickly.

Research shows that people form impressions about a leader’s competence in as little as half a minute. This means, within seconds, listeners will decide whether you are trustworthy, and they will do it based on your body language and vocal attributes. What you say and how you say it are equally important.

The good news is that there is plenty of hard evidence that explains how you can give the appearance of confidence and competence — even if you’re nervous or timid on the inside.

How to Look Confident

Make eye contact. Making eye contact is the first step to building trust with your listeners. “Eyes play a key role in human social encounters,” according to one research report. “When humans observe others’ faces, eyes are typically the first features that are scanned for information.” There’s a simple way to get better at this, but it takes a little work: Record yourself practicing your presentation in front of a small audience. Watch the recording, noting all of the times you look at your slides instead of at your audience. Practice, and record again. Every time you do, try to spend less time talking to the slides and more time making eye contact with your listeners. Rehearse until you have the presentation down cold.

Keep an open posture. Open posture means that there’s no barrier between you and the audience. This includes your arms. An uncomfortable speaker might unconsciously cross their arms, forming a defensive pose without being aware that they’re doing it. Confident speakers, by contrast, keep their arms uncrossed with their palms turned up.

But your hands and arms are just one barrier. There are others to eliminate.

A lectern is a barrier. Stand away from it. A laptop between you and your listener is a barrier. Set it to the side. If you keep your hands in your pockets, take them out. An open posture takes up more space and makes you feel more confident. If you feel confident, you’ll look confident.

Use gestures. Confident speakers use gestures to reinforce their key points. One study found that entrepreneurs pitching investors were more persuasive when they used a combination of figurative language (stories, metaphors) and gestures to emphasize their message.

Find areas of your presentation where gestures will come across as natural, and use them to highlight key points or emphasize a concept. If you’re listing a number of items, use your fingers to count them off. If you’re talking about something that’s wide or expansive, stretch your arms and hands apart. One analysis of popular TED speakers, like Brené Brown and Tony Robbins, found that they tend to bring their hands to their heart when sharing personal stories. Your gestures will reflect your feeling toward the topic you’re discussing and invite the audience to engage with you on a deeper, emotional level.

How to Sound Confident

Eliminate filler words. Avoid words that serve no purpose except to fill the space between sentences. These are words like um, ah, like, and the dreaded, you know? Excessive filler words can be irritating to listeners, and make speakers sound unsure of themselves. Eliminating them is also one of the simplest habits to fix.

Start by studying the verbal delivery of sports commentators. The ones who are at the top of their game rarely use filler words. Instead, before speaking, they think about what they want to communicate next, and deliver their comments precisely and concisely. Listen to Jim Nantz calling a golf event, Bob Costas calling the Olympics, or Al Michaels calling a football game for great examples. After years of practice, these announcers have become skilled at delivering just the words they want you to hear. How did they get there? By spending hours in front of the television, reviewing videos of their performances.

Use this same strategy. Turn on the video or microphone of your smartphone and record yourself presenting. Play it back. Your goal is to gain awareness around the filler words you use most. Write them down, and practice again. When you catch yourself about to use one, err on silence instead to develop a smoother, polished delivery.

Take time to pause. Most people use filler words because they’re afraid of silence. It takes confidence to use dramatic pauses. A pause is like the period in a written sentence. It gives your audience a break between thoughts.

A recent story in the New York Times, for example, calls attention to the silence in between notes of a classical music piece, explaining why short pauses draw so much attention. As social beings, we are hard-wired to pay attention to breaks in the flow of communication. “We recognize the pregnant pause, the stunned silence, the expectant hush,” the author writes. “A one-beat delay on an answer can reveal hesitation or hurt, or play us for laughs.”

Pauses are interpreted as eloquence — in music and in public speech. A simple way to learn the power of the pause is to choose one or two phrases in your next presentation that express the key message you want to leave your audience with. Pause before you deliver those lines. For example, “The most important thing I’d like you to remember is this…” Pause for two beats before you complete the sentence. Whatever you say next will be instantly memorable.

Vary your pace. Confident speakers vary the pace of their verbal delivery. They slow down and speed up to accentuate their most important points.

Audiobooks are recorded at a moderate pace of 150 to 160 words per minute. It’s slow enough to be understood, but not so fast that the listener has a hard time keeping up. TED speakers, similarly, speak around 163 words per minute, right in the sweet spot.

But here’s the trick. The best speakers speed up to around 220 words a minute when they want to embellish a certain story detail and keep listeners engaged. When they want to accentuate a certain message, they pause, then deliver their words at a slower pace.

Take TED speaker and human rights attorney, Bryan Stevenson. He delivered a presentation that earned the longest standing ovation in TED history. Stevenson is a masterful public speaker. He constantly varies his pace to keep the audience riveted. In one anecdote about meeting civil rights hero, Rosa Parks, Stevenson sped up when he rattled off a long list of what his non-profit intended to accomplish.

I began giving her my rap. I said, “Well, we’re trying to challenge injustice. We’re trying to help people who have been wrongly convicted. We’re trying to confront bias and discrimination in the administration of criminal justice. We’re trying to end life without parole sentences for children. We’re trying to do something about the death penalty. We’re trying to reduce the prison population. We’re trying to end mass incarceration.”

Stevenson then dramatically slowed down the pace of his speech to deliver Park’s response: “She looked at me and she said, Mmm mmm mmm. That’s going to make you tired, tired, tired.”

The audience laughed, touched by the story. Stevenson’s varied and controlled delivery made a story that could have been dry and predictable, poignant and humorous. He never leaves his delivery to chance.

How can you master this skill? Let the story you are trying to tell guide you. Don’t force it, but if there’s a part in your presentation or speech where it makes sense to rattle off a series of words or sentences — perhaps a section in which you need to run through a list of details — try speeding it up. Then, slow it down as you approach your main point.

It’s the rare presenter who’s mastered all six principles of confident speaking. In fact, many speakers are unaware of them. Now that you know the secrets to looking confident in front of a crowd — practice, practice, practice. Don’t be hard on yourself if it takes more time than you expect. Some of these tactics will take a couple of run-throughs to get right, while others — like pacing — require hours of work and advanced delivery skills to nail down. Keep at it. There is nothing more influential than the power of your presence matching the power of your ideas.