Regarding remote scams, seriously:

If someone wants something over the phone or the Internet:

If you don't know them, just refuse without engaging.
If it seems that you know them, get back to them yourself, preferably in another way (over a different channel).

For e-mail, the first point means:
do not open anything from the message and do not reply.

Keep in mind that:
voice is easy enough to fake convincingly;
a phone number (caller ID) is also easy enough to fake for incoming calls;
any advertisement may be fake and it is easy enough to make it seem good.
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I believe each such tactic must be as simple as possible to have a hope of being useful.