1. Pay attention to transitions among slides. Make sure they are connected fluently.

2. Think in bigger pictures. Don't get into too much detail unless you need to.
When you're not sure about whether or not you need to include something, think whether it will confuse the audience if the discussion is missing. Or if it's your research contribution you definitely want to include it. Do not go too low level.

3. Handwave a little on unimportant contents, or even skip them.