For the last several talks I've given, I've printed all my slides and taped them up to the wall.
Then I rehearse the talk once with a marker and write notes as I work out the wording.
Then I walk through the talk with someone else in the room, more explaining the slides and the narrative than actually rehearsing, taking notes while I do that.
Then I collect my notes and practice from that.
I find actually rehearsing to be incredibly difficult (it's awkward, in the same way that narrating a screencast is awkward, but magnified), and while this isn't a perfect substitute, it's drastically better than just trying to write out everything I'm going to say, or, worse, just throwing slides together and hoping.
Then I rehearse the talk once with a marker and write notes as I work out the wording.
Then I walk through the talk with someone else in the room, more explaining the slides and the narrative than actually rehearsing, taking notes while I do that.
Then I collect my notes and practice from that.
I find actually rehearsing to be incredibly difficult (it's awkward, in the same way that narrating a screencast is awkward, but magnified), and while this isn't a perfect substitute, it's drastically better than just trying to write out everything I'm going to say, or, worse, just throwing slides together and hoping.