How do I use mental rehearsal to learn choreography?
Close your eyes, play the music if you can, and run the routine from the inside — feeling each weight shift and seeing each shape in time with the count — rather than watching yourself from outside like a video. Done in real time, it uses much of the same circuitry as moving, so it adds repetitions when you cannot dance and it shows you exactly where the sequence goes blank.
From the inside, in time
The rehearsal that transfers is first-person and at tempo: you feel the push into the floor and the arm arriving on the count. Watching a mental video of yourself from the front is less useful. If the music is playing, keep to it; if not, count out loud under your breath.
When the picture goes blank
That is the information. A gap in the mental run marks a section that was learned by copying and never encoded. Drill that section physically next; the mental run will then go through it.
When to do it
Last thing at night, for the consolidation; on the way to practice, to start warm; and right before a run in the room, once, as a preview. Two or three minutes each. It is a supplement to dancing, not a replacement, and it works well on material you have already danced at least a few times.
Questions people ask
Should I move slightly while I rehearse mentally?
Small marking with the hands or the feet helps many people and does no harm. Full marking is a different exercise and also useful.