Cue: I say the word "clearly", "hopefully", or "obviously".
This definitely doesn't always indicate rationalization, but I say one of those words (and probably some others that I haven't explicitly noticed) with much greater probability if I'm rationalizing than if I'm not, and saying them fairly reliably kicks off an "ORLY" process.
Oooh, I just realized: if you can pick out words like this when you're writing, and you can code in your text editor, then your computer can catch this cue for you. (like writegood-mode in emacs). I've had this prevent ugly sentences in technical writing, but catching "rationalization words" in written sentences would also be useful when, say, writing a journal, or writing down an argument.
More awesomely, the highlighting is immediate in that mode, so you get tight feedback about the sentences you're typing.
How do you notice when you're rationalizing? Like, what *actually* tips you off, in real life?
I've listed my cues below; please add your own (one idea per comment), and upvote the comments that you either: (a) use; or (b) will now try using.
I'll be using this list in a trial rationality seminar on Wednesday; it also sounds useful in general.