I almost always pick something like "What's your favorite color?" and answer with random noise (say "a3tcuh487wchaowiudh23doch3298ahraui"). The rationale is that if I forget my password, I'll likely forget the secret question as well. I only want the secret question to be as hard, or harder, to guess than my password.

I wonder though, if the human at the other end will accept "just a bunch of letters and numbers" as a correct answer.