>Assume everyone asking for such things are scammers.

That's excellent advice, and everyone should follow it. Unfortunately some banks disagree and will cancel your credit cards when you fail one of their fraud check phone calls.

> And guess what, the only way to be sure that it’s your bank you’re talking to, is to call them yourself. Period. Some callers tell you details of your account as a way of identifying themselves.

There's a scam in the UK where they call you, and ask you to call them back. You hang up, then pick up the phone and dial the number. But because they initiated the first call the line doesn't clear until they hang-up, and they don't hang up while you're dialling the number. (And the sometimes play recorded ring tones before they "answer").