1. Create a structure ( a skeleton with the main points)
2. Write absolutly everything that comes into your mind.
3. Find the core/key values ( what´s the outcome or takeaway that you want to give to people )
4. Paraphrase ( don´t try to remember everything, your audience won´t either)
My trick to remember is:
"I think of my speech as If I´m taking the underground to get somewhere, I take the train in "Green Park" to go to "Vauxhall", in order to do that, I know the train first have to stop at "Victoria" and "Pimlico"."
Same with your presentation, if you have a clear structure in your mind, even if you get lost at some point, you know what´s the next "station" where you have to stop.
If it makes sense to you it´ll do for the rest!
Try this and let me know how it goes!