In a professional context, tell your boss that you can't and won't work without the required information. Or improvise with fake/mock data.

If I’m waiting for input from someone, I immediately create a future to-do that’s of the form of either “do stuff with input received from X” or “follow up with X if I haven’t received their input on Y”.

Their actual input can be either attached to the to-do on receipt, searched up in email/slack/meeting notes/etc as needed, or entered in a notetaking app on receipt — depending on what my current getting stuff done stack looks like.