If you do live coding and it works well, developers will love you.
If you do live demos, make sure your talk is fine if they don't work and that they don't need internet.
Slides should be high contrast and easy to read from far away.
Try to make your talk a story.
Focus on messages, don't do tutorials.
Focus on a few points rather than squeezing in everything.
Don't put bullet points on your slides.
One statement, maybe two, per slide, not more.
Entertainment is at least as important as content. This does not always mean just adding memes or cat pictures.
Sometimes just content is also pretty amazing, if you can be sure to not lose the audience.
Pictures, pictures, pictures. For illustration, for entertainment.
Engage the audience, ask questions, make them stand up. Don't make them feel stupid.
Talking fast is fine, if your audience is good at English or you are being live translated. Make sure to speak clearly though, so people understand you.
Be nervous, but don't let that keep you from giving a kick-ass presentation.
Always be excited.
Don't apologize for your slides.
Don't apologize for skipping a slide or telling things out of order.
Don't apologize for finishing early. Actually, try to finish early.
Take off your lanyard before starting your talk.
Make sure your display settings work beforehand.
Use a presenter view whenever possible. Having a timer, notes and the slides there really helps me not to panic.
If you use the browser of terminal, bump up the font size to what you think is appropriate for the room and then a little.
If you run into technical issues during your talk, do not stop talking to the audience. They losing interest is the worst thing that can happen.
Make sure there is a display adapter for your computer.
Bring a remote for going through slides.
Make sure your laptop won't go to sleep. On Mac, install Caffeine from the app store.
Drink something during the talk. I constantly forget that and regret it later.
It is always better to have someone introduce you rather than introducing yourself. However, that is obviously up to the conference.
When you have a say in the time slots, 25 minutes is usually better than 45.
Make a reference to the country you're in, people love that.
If you reference something, make sure people know the reference. If you quote a TV show, maybe make sure people in the country you're in actually know the show. Don't speak of "soccer" in South America, don't speak about "football" in the US.
Don't be condescending. Don't make fun of people unless it's Nick Sutterer. Don't make fun of programming languages, etc.
Don't be sexist, racist, etc. Should be pretty obvious.