My favorite is Tip #36: Integer numbers less than ten should be written in long-form unless they are measurements with associated units or are within a range (e.g. 2-5). For example, you shouldn’t write, "There were 4 cats that scratched the researchers more than all others." For those of us that are old enough to recall life before we started publicly broadcasting 144-character reports on the nuances of our breakfasts (Forget my diet; I'm having 2 bowls of cornflakes this morning!), these low-integer numerals are particularly grating.