Cover Your Assets
When you get to the editing stage, you'll focus on assembling a tight movie, with no scenes that will lose your audience's interest. But during the shooting, you want to make a point of getting plenty of coverage. Linger at the end of scenes--don't just quickly stop recording when the action ends. Take a few minutes to shoot the scenery, the reactions of people around you, or objects that catch your eye but may have nothing to do with the subject of your video. You want to go into the editing stage with more than enough footage to work with, because in most cases you won't be able to go back and reshoot something. Having a lot of coverage can wind up being essential when you need to add a few seconds of footage in order to maintain your movie's timing and rhythm.
Dumpster Diving in iMovie
Once you're done shooting, you need to import your footage and begin putting together your movie. As you chop, crop, and rearrange your clips, you can lose track of what the footage looked like originally. This can be problematic when you inevitably want to go back and try a different combination of clips. Fortunately, iMovie offers a few methods to retrieve your footage.
Probably most useful method is to invoke the Undo command. iMovie supports 10 levels of Undo. Be forewarned, however, that the counter resets if you close your iMovie project and then open it again.
Another method is to restore an original clip. As you make edits, iMovie only records the changes that have been applied to the clip--it doesn't actually split the clip file that exists on your hard disk. So even if you've taken a long clip and split it into a hundred snippets, you can still select a snippet and choose Restore Clip Media from the Advanced menu to go back to the original (the other 99 snippets remain in place).
The only time this becomes a problem is when you throw clips into the Trash. Unlike the Trash in the Finder, you can't open iMovie's bin and grab a discarded clip like a half-eaten banana. Once it's thrown away, consider that clip gone. However, at this point you can still use the restore command on another snippet to get the full clip. But if you use the Empty Trash command at any point, then the clip is gone gone - emptying the Trash prompts iMovie to delete the affected snippets from the clip file on the hard disk.