Over the last six months, I've attended 18 conferences and heard over 30 keynote sessions, mostly about software development and management. I think I now know all the secrets of a successful keynote speaker. It doesn't look so difficult to become one. Here are my thoughts.
Be obvious! Don't take a chance by suggesting something new. It's risky and some people may disagree with you. That's not good. The goal is to have everybody in the room completely agree with what you're saying. That's how you make a good speech. The audience will be comfortable and relaxed, and you will have no risk of being questioned afterwards. A few safe headline examples: "trust is very important" or "software must be stable." Everybody will be nodding their heads—that's all you need.
Joke! You must make them laugh. You must open with a joke and continue with many of them. Prepare them carefully. Just Google "good keynote jokes" and use what smart people recommend. A well-prepared collection of jokes is much more valuable than the content you will be talking about. Nobody will remember the content, but the jokes will definitely be re-tweeted. When a good speaker is talking, the room is laughing every 60 seconds.
Swear! Don't be too formal and boring, show a slide with a picture of a naked butt every once in a while. Everybody will understand that you're not only a speaker but also a good friend. Also, your language should be rather loose. Pretend you're talking to a friend over a pint of beer. Remember, the goal is to be funny.
Repeat! Always bring the same content with you, to all conferences. It's easier for everybody. First, conference organizers will know for sure what will you be talking about. They can even watch your 4-year-old video-recorded presentation and see exactly what words and slides you're planning to use. Second, you won't be nervous, since you'll be saying the same jokes over and over again. Everybody wins.
Kitties! Cute kitties. We all love them! Attach them somehow to your content. It is not really important whether they are related or not. You must show love. Instead of cats you can use a picture of your 2-y.o. daughter or yourself in a primary school. It has to be something sweet and adorable.
Keep talking! A good keynote speech fills the entire 60 minutes, leaving absolutely no time for questions. Actually, a perfect speaker will be interrupted after the 145th slide and will say that if anyone wants to know more, there is always a place near the restroom, let's go there and continue. Thus, be focused on your slides and try to avoid questions at the end—they may create a negative impression of you if you mess up answering their questions. They came to listen to you, not to ask questions—keep talking.
On a more serious note, I'm very disappointed by what I've seen in almost all conferences so far. These keynote speakers are in most cases just making money, delivering the same "fun" again and again. They make $2-3K a speech and we, the listeners, get absolutely nothing new out of them.
Conference organizers keep inviting them, just because of the names. And we keep attending that conferences also just because of the names. But do these names really mean anything? I don't think so. These guys are, in most cases, just retired losers with good presentation skills.
It would be much better to spend the money conferences waste on the big-names for training practical speakers from the trenches, with really fresh and interesting content. As far as I understand, conference organizers are just too lazy to do that. It's just easier to buy a "proven" clown.