For reading music:

The lines on the treble clef:   Every Good Boy Does Fime.
The spaces on the treble clef:   Spells "FACE."

The lines on the bass clef:   Good Boys Do Fine Always.
The spaces on the bass clef:   All Cats Eat Good. (Not very grammatic, but it works).

When you have the two clefs together (as in piano music), the line between the two clefs—in the middle, so to speak—is Middle C.

Don Firth

P. S. Now, if we just had a good mnemonic to help us remember the mnemonics. . . .