When I teach executive education classes at Harvard, I set a deadline for students to submit their final slides. The deadline is about two weeks before they're required to deliver their presentations to the class. By forcing speakers to finish their PowerPoint slides two weeks early, it offers plenty of time for speakers to rehearse.

Once students send me their final decks, they often ask me, "How much should I practice?"

Well, I once interviewed a scientist who practiced an 18-minute presentation about 200 times before taking the TED stage. Jill Bolte Taylor's "Stroke of Insight" attracted millions of viewers, making it one of the top TED talks of all time.

Here's the good news--you don't have to practice 200 times. Bolte-Taylor had months to prepare, but in the real world, there's a lower number that is effective and achievable.

The ideal number of practice sessions is 10.

If you rehearse your pitch or presentation 10 times, you will grow more confident, and your delivery will show it. Remember, these are full rehearsal sessions where you run through the content from start to finish. It means your slides should be 80 percent complete, leaving a little room for changes as you talk through your presentation out loud.

Don't worry. You don't have to be perfect on the first try. The following rehearsal outline should guide your practice sessions.

Part One (practice sessions 1-3).

The first three practices are simply intended to help you get comfortable with the content. You'll catch yourself looking at notes, forgetting your place, and making changes to your deck like moving slides or deleting some entirely. Think about how you're expressing the ideas of each slide. Is there a clearer, more concise way to say it? Feel free to use a stopwatch if you'd like, but timing is more critical in the next session.

Part Two (practice sessions 4 and 5).

Now you need to get serious about using the stopwatch if you haven't done so already. If you're given 18 minutes for a TED Talk (or seven minutes in my classes), stick to time. If you go over in practice, cut stuff out. Minimize your reliance on notes with each practice. Memorize the first two minutes of your presentation, the conclusion, and the main idea of each slide so you can make eye contact with the audience instead of reading from slides.

Part Three (practice sessions 6-8).

Deliver the full presentation all the way through. No stopping. If you forget your lines, improvise and keep going. Record these presentations. Watch the video to catch annoying habits like using too many filler words or reading from your slides.

Part Four (practice sessions 9 and 10).

Now it's time to mimic real-world conditions to boost your confidence. Increase the stress level by delivering the presentation in front of friends or peers. If that's not possible, at least find an empty meeting room or office where you can stand up and deliver the presentation with a display and a clicker to advance the slides. Think about your vocal delivery and the gestures you make. And don't forget to smile.

When I'm invited to give keynote speeches of 45 minutes to an hour in length, I spend many hours on research to make my presentation relevant to the audience. But once I'm happy with the content and the slides, I make time on my calendar for a minimum of 10 practice sessions (usually once a day for the two weeks before the event).

Since most speakers don't commit to practice, you'll stand out by making the time to rehearse and refine your presentation. Above all, you'll speak with the confidence you need to make a strong impression.