1. Be careful in your proposal that you are not aiming to cover too much ground for your alloted time.
  2. Use video embedded in your slides to demonstrate what you are talking about as you are talking about it.
  3. When presenting code, seriously lower the opacity in any part of the example that you are not talking specifically about at that moment. So for most code examples you will have several slides, with different parts focused based on your talking points.
  4. Write presenter notes and use them as a fallback.
  5. Don't be boring.
  6. Practice at least a few full run-throughs. Try at least one with someone who has no idea what you are talking about and they will give you incredible feedback to simplify your message.
  7. Have friends with expertise in the subject read through your slides to catch any mistake or opportunities to improve the material.
  8. Try not to repeat what has already been said well by other people in presentations available online. Share your unique perspective.
  9. Consider that if the talk will be posted online, your largest audience is likely to be people who view it on the web.
  10. Pause after showing a code snippet (preferably three lines or fewer) so the audience has time to digest it.
    Suggested by @james
  11. Aim for the middle.
    This is a variation of "know your audience" but I always consider it a success when I speaker feedback shows both "too advanced" and "too basic" in about equal numbers. Avoid the urge to wow with technical excess or to dumb it down too much.
    Suggested by @gwcoffey