I write an outline of my points (not a word-for-word script, although I do include word-for-word key phrases) that aren't obviously on each slide,and then practice practice practice until I can hit my main points without looking at the outline.

Also, if I seem to be stuck on a specific slide, sometimes I include a few initials standing for key points in tiny font in the corner of my slide, to help me remember. I don't rely on it a lot, but just having it there is a comfort. When asked what's it's for, I casually and truthfully answer that its a memory device so I don't leave out anything that may be important to the audience.