(Read also this post (in French) on my professional blog for a tad more details.)

• Style. Determine from the outset what will be the most appropriate format and tone for your presentation, i.e. formal or informal, friendly or "tightly" professional, etc. All styles are not necessarily good for all contexts. Make a thoughtful choice.
• Subject. Have a clear mind and a precise idea of the story you want to tell. Word of caution! To do this well requires effort!
• Structure. Your presentation is a story to your audience. Tell a story that people will remember. Tell it with a beginning, a middle and an end.
• Simplicity. The average audience will only retain two or three ideas from your presentation. Know which ones you want them to remember and help them remember them: repeat your key points often!
• Save it! [Note: the French version is Savoir. I couldn't find a more direct translation in English that started with an S. Give me a point for the effort! ;-)]. Define yourself an objective; know your audience (level of knowledge and interest in the matter) and the context of your presentation including all environmental aspects of it (room, layout, time of day, equipment), and know your stuff Then, save all this to memory! And please don't underestimate the technical risks... Murphy is never very far.