HOW DO YOU GET A SINGLE FRAME FROM IMOVIE COPIED TO IPHOTO?

This is probably not the preferred method. But this is what I came up with

1. Switch to full-screen playback in iMovie (Apple key + letter g)
2. Move your mouse to the bottom of the screen, and skim across that video until you get to the EXACT frame you want to copy.
3. Now you are going to take a screenshot. Hold down the Apple key + Shift + number 4. It will be hard to see but the cursor will change shape to a circle and cross-like target.
4. Move the cursor up to one corner (say the top left) and drag diagonally across and down to the opposite corner (lower left).
5. Let go of the mouse button when you reach that corner. You might here a camera sound at that point (that's the Mac's way of saying you made the screenshot).
6. Now quit iMovie and go to the Desktop. If your Desktop isn't too crowded with folders and other stuff there should be a picture there with a title beginning with the words Screen shot.....(and the date and time).
7. Drag that picture down to the Dock at the bottom of the screen and drop it onto the iPhoto application icon. That will import the picture into iPhoto.

elikness's method above works well however this is the other way, courtesy of AppleMan:

https://discussions.apple.com/thread/3064570

And I think AppleMan has me beat in smallest number of steps too! 😁 I think MPEG Streamclip is going to be simpler all around.