"What's the best way to prepare for a big presentation?" I was recently asked this question by Logan LaHive, the Managing Director of TechStars Chicago.

He had invited me to come in and speak to the founders at TechStars -- one of the leading accelerator programs for early-stage companies. The program culminates in Demo Day, where founders give a 5-10 minute pitch in front of investors and community members, with the hopes of getting funded.

With Demo Day less than a week away, LaHive was hoping I'd share some insights for the founders on how to prepare for that big presentation.

For me, as a CEO who's spoken all over the world for the past few years and given over 100 talks to audiences as small as 10 people and as big as 1,000 -- I knew the answer almost immediately.

The #1 thing I do to prepare for a big presentation is to record myself.

It's a technique I learned from my entrepreneurship professor in college -- Troy Henikoff, who originally founded TechStars Chicago and today runs a venture firm called MATH. I remember him recommending this tactic in class to me about 10 years ago, and how much it's since impacted my public speaking thereafter.

Recording yourself on video -- and then watching yourself -- is the quickest, surest, most fool-proof way to improve your pubic speaking skills. I guarantee that in a matter of minutes, you'll see exactly what you need to fix. And you'll fix it immediately. It's far more effective than practicing in front of other people.

I turn on the "Photobooth" application on my computer, click the "Video" button, and hit record. Then, I force myself to do the whole talk through. The first time, it's usually pretty painful. There are long gaps as I struggle for what to say, or countless "ums" that I know I shouldn't be there.

Aside from helping you notice the obvious things you need to fix, recording yourself on camera is the most effective means of improving your public speaking for two other reasons:

You're forced to practice the talk top-to-bottom.

Typically when I practice a talk, I have the tendency to practice it in chunks. After all, it's exhausting to rehearse a 40-minute keynote all the way through. But this also means I'll often only practice the parts of the talk I'm most familiar with. Maybe it's just the intro. Or maybe it's just the main thesis of the presentation that I could talk about in my sleep. But when you record yourself and run through the talk top-to-bottom, you're forced to figure out the transitions. You realize that the intro is way too long, or your conclusion is too abrupt. You realize there's definitely a section of your talk where you sound like you're rambling -- clearly you don't know your material for that section as well as you should.

You're spurred to action more quickly than ever before.

When you watch a recording of yourself giving a presentation, you become your own worst critic -- and that's a good thing. You see the weird thing you do with your hands. You cringe, and now you'll never do it again. For me, personally, I distinctly remember preparing for a talk a few years ago, and being horrified that I said, "You know?" almost every three to five sentences. It made me look unsure and that I didn't know what I was talking about. As a result, today, I almost never say the words, "You know?" in one of my presentations. If anyone else were to have said given me that same feedback after watching my talk, I'm not sure I would've changed my behavior so quickly. But when you see it yourself, the proof is in the pudding. You react immediately, fix it, and vow to never do it again.

I usually run through and record a talk three to four times, all the way through. Sometimes more, sometimes less. If this sounds like torture to you, I understand. (Trust me, I hate even listening to the sound of my own voice on my voicemail recording.)

But, if you're looking to improve your public speaking skills by leaps and bounds, and you're short on time to do it -- give recording yourself a shot.

Think you'll be pleasantly surprised by the difference it makes.