Dear Mike and all,
W.r.t. the flat of the needle; another easyish way to remember might be to think of where the flat part is butting up against its little housing. I find this logic works for me, thinking of how to get that needle in there nice and snug. Of course then on some machines it is still possible to thread the thread the wrong way. I like your way of saying that the thread always enters on the Not Flat side. That also works.
My Anker Phoenix is currently out of commission with a thread jam to end all thread jams. I am beginning to wonder whether I goofed with that. It is a round shank needle. So is there a rule of thumb with a round shank needle? Is it always long groove towards the front, and thread therefore -in- the long groove side of the needle? Just wondering if there is a catchy way to encode this in my memory as I flail about from machine to machine. :-)