As a tech lead or eng manager, you so frequently get request from above or from other teams to drop what you are doing and work on this thing they need, now.
"What is the impact of this work you're asking for?" If the impact is unclear: sorry, but we can't do the work. Why would we? Just this question made the requester realize half the time they just think it's urgent, but don't know what the work will actually result in.
"Do you have a spec that is agreed with stakeholders?" A writeup answering the "why" and the "what" that is signed off by relevant business folks. I've seen so much engineering work thrown out as later the business goes "that's not what we wanted, why didn't you tell us?"
"We're not committing to any work before we have done a rough estimation." With #1 and #2 done, many stakeholders will come and say "drop what you're doing, this is a 3-day work we need ASAP." Hold your horses. You don't make estimates: the team doing the work does...
Make the cost of dropping what you're doing very clear. This cost is always forgotten by the person coming with the request. But it's a relevant one: wrapping up work, onboarding to the new work, then later onboarding to the old work. Plus a hit on morale for a sudden change!