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.

- WFR (waiting for response/reply (from)) {person} re {subject}

- FUO (follow up on) {subject}

Or, if I first have to do a task, then get a response, I surround the task in parentheses instead of crossing it out to indicate that I did it but I'm waiting for something else to happen (usually for someone to call back or something). For example, if my task is "call helloworlddd", and I do, but you're not home and I leave a voicemail, then

- call helloworlddd

becomes

- (call helloworlddd)

and when you finally call back I cross the task off.