What do you guys do to prevent mirrors from fogging, or at least getting them clear to shave?

I've heard wiping shaving cream on them then wiping it off keeps it clear. I tried that a few years ago and it didn't work at all.

Even after a shower and I try wiping the fog off with my towel, I can't get it cllear enough to shave by, and it fogs back up within a minute.
I bought a mirror that claimed to not fog, that was a lie.

What are your secrets?