[iamscanner]

This is not-super-secure, but in a lot of situations I just use a rule like "third character of first word + second character of third word + first character of fourth word", and so on. You end up with gibberish most of the time, but at least you're not going to let it slip in conversation (and as long as you remember the rule and don't pass that around, you're hopefully okay).

[exogen]

My strategy is to pad the real answer with the same two words for each question. For example, "purple 12345 banana", "purple Smith banana", etc. Not perfect, but it should defeat even the best would-be guessers.