You know, I posted a joking response, but forgot to post the question line I use: "How are you sleeping?" It may not be great, but that "reduced need for sleep" often suggests whether or not to r/o bipolar. I mostly deal with people who have anxiety problems, which can look a lot like mania sometimes. If they say they're not sleeping, "but I don't seem to need it," that tells me to do a little more prodding. If they say they're not sleeping and can barely function, we can move on...
Not great, but sometimes somewhat suggestive...