Saw the following on the site of screenwriter John August (Go, Corpse Bride, and others).  I’m a regular practitioner of index cards/post-its when breaking a story, and he makes some good points.

1. Keep it short. Maximum seven words per card.
2. A card represents a story point, be it a scene or a sequence. You don’t need a card for every little thing.
3. Keep cards general enough that they can be rearranged. (“Battle in swamp” rather than “Final showdown”)
4. Horizontal (a table or counter) often works better than a vertical (a corkboard).
5. Post-It notes make good alternative index cards.
6. Consider a letter code for which characters are featured in the sequence. Helpful for figuring out who’s missing.
7. Most movies can be summarized in less than 50 cards.
8. Cards are cheap. Don’t hesitate to rework them.
9. Consider a second color for action sequences. Helps show the pacing.
10. Write big. You want to be able to read them from a distance.