iMovie Shortcuts:

cmd + b = split clip
v = voiceover options
cmd + c = copy
cmd + v = paste
cmd + z = undo
space = play/pause

Other Options to Remember:

detach audio: right-click on clip, "detach audio"

crop/fit clips, change speed, change colors, stabilize, & more: click on clip & click options in viewer

 

Ryan's Old iMovie Help