Here are some of Chris's tips for delivering a TED Talk:

Use fear as your motivator

[Public speaking] is terrifying and I think it does go back to this fear of humiliation. The thing is, now, you're not going to be thrown out of the village and never eat again. Most audiences are actually really welcoming. First step for your rational mind is to say "Okay, let's be reasonable here". The second is, what fear is for. Fear is motivation to act to avoid that fearful thing happening. In this case there are specific actions you can take.

Be prepared

The single most important thing is to actually prepare for your talk. A lot of us assume that the way you get ready for a talk is to write down some bullet points, psych yourself up, and then go out there and wing it. If you're nervous about a talk, rehearse it. Rehearse it in your room, rehearse it with a few friends, record it if you like, on your smart phone. Over that process you can move that nervousness into a feeling of excitement. It is a very close feeling between those two and that means you can bring energy with you onto the stage, which is a good thing.

Decide how you are going to approach it from the start

When you talk to TED speakers, there are two different paths that people take. There is the memorisation path and then there's the speaking in the moment path and they're very different types of preparation, I think it is really important to decide early on which path you are going to take.

The wonderful thing about memorising is that you can get every word exactly the way you want it, you craft the perfect talk that efficiently shares your idea in the amount of time. The trap is, apart from the possibility of outright freezing, is that you end up sounding a bit robotic, and that is the last thing you want. Really the cure for that is to know it so well that the talk is in you. When you know it as well as you know the song happy birthday. When you're singing someone happy birthday, you're not trying to remember the words, you're looking at them and you're full of love and wishing them joy. If you can get to the point where you know your talk so well that you're not struggling to remember it, but you're just focused in the minute and just talking to people. That is a very powerful way of giving a talk.

But the other way of giving a talk is to not memorise it, to speak from a carefully constructed talk, but then the other trap is that you end up rambling, you miss out key parts or you way over-shoot.

So again, I think the key is to prepare a lot, to actually give the talk many times, and in the process you’ll probably unintentionally memorise the talk anyway. There are two different ways of constructing the talk, not so much two different ways of giving the talk, but either way when you give the talk you know it, but you're present in the moment, communicating to the audience. But don’t get trapped in the middle, don’t half memorise it, it's a disaster.

Speak for others; speak for your idea

One of the most beautiful things that [Monica Lewinsky] did was write on her script "This matters." I think that's actually really powerful, is to remind yourself that it's actually not about you, you're doing this in service to an idea. She wanted to speak out, she wanted to highlight the issue of cyberbullying. She had been Victim Zero almost, on the internet and had seen the stories of teenagers committing suicide because it is so intense in this world of social media and text that we are in. It can really destroy people without really knowing what they're doing. She wanted to speak out on this and I think that was a big part of it that kept her going.

Remember: the audience wants you to do well

If you're nervous, I've often seen audiences embrace and love speakers who are nervous. I find that there's something authentic about it, sometimes they even say, "I'm a little nervous, but actually I am really passionate about this, so bear with me. We're going to get this through." People, even when they freeze, audiences clap and say, "Take your time, it's okay". It always feels worse for you on stage than to the audience.

Stress. It makes your heart pound, your breathing quicken and your forehead sweat. But while stress has been made into a public health enemy, new research suggests that stress may only be bad for you if you believe that to be the case. Psychologist Kelly McGonigal urges us to see stress as a positive, and introduces us to an unsung mechanism for stress reduction: reaching out to others. She also suggests that seeking to do meaningful things enhances our lives, even if that involves taking on a stressful activity.

Do push ups before going on stage

We had a TED where we had Edward Snowden, the whistleblower, who was very much in the news a couple of years ago, and he gave a talk via telepresence robot and that was a little bit nervy, but then we felt like we had to give equal time to the NSA. So I was due to interview them over a video connection and I just felt like the stakes were quite high in this one, I certainly felt quite nervous beforehand. I found myself physically shaking coming into this and I just stopped in the corridor and started doing press ups and I kept going and I kept going. It was wild. I ended up doing 30 or 40% more than I would usually do and it was pure adrenaline. Adrenaline is this drug that is telling your body to fight or fly. You have to work it off, because it is that that is causing the shaking, and if you can burn it off before coming on stage it certainly calms you down.