Lewski709, my mom has had a few--although each person is different, I can tell you a few things that told us she was "over the edge" versus her usual "tap dancing next to it". (pardon the sarcasm, this is something I've always lived with!) On a typical day she would be in a fantasy world, but when she's had a breakdown, she would be completely gone. Things like running around the neighborhood in her nightgown (not a pretty picture). Taking off the dog's collar because "he deserved to be free". One time, when I called her, she wouldn't talk on the phone or turn on the lights because "they" were listening in and watching her. These behaviors were beyond her usual looniness, and didn't clear up with time or, say, a good night's sleep. On the other hand, even on a good day, she has difficulty sleeping, can't follow a conversation, etc. We (my siblings and I) were actually relieved after the first breakdown, because we thought, Finally! she'll get the help she needs!" Joke was on us. The hospital says it takes an average of 6 times before the patient realizes they need the meds permanently. It's been 4...she isn't below average yet!
I hope that helps, a little, feel free to ask any specific questions if you like, I've lived with this my whole life.