In addition, from being on both ends, asking for what the priority is for a new ask is incredibly important. It not only gives you cover for when other things slip due to the new ask but forces the manager to consider the slippage (always good to remind them as well) and be clear if this is a "drop everything" or "when you have time" task.
I've been lucky to work at some places that are very clear about their asks and also are very open to you coming back and saying "So I looked into this and to do it the way you want it will take 2 weeks or I can get it 90% of the way there in <1hr". Being open to that back-and-forth as well as surfacing the different time estimates are both important and can benefit everyone. It's sometimes hard to know, as an employee, when asked to do something if it's important that it be "pixel perfect"/"exactly to spec" or if it was just an idea someone had who would be happy to settle for an alternative that takes a fraction of the time to complete.
As a manager I've found how important time-boxing certain tasks are and asking people to circle back if it's taking longer or if they later realize the task is bigger than either of us thought. Sometimes we have to take the time and sometimes it's something that we need to think about a lot more before we dive in. The worst is when you get busy with something else then find out the next day that someone spent all day on a task you thought would take <1 hour. Sometimes it's a misunderstanding of what needs to be done, sometimes it's the person trying to match exactly what you asked for even if an alternative would be way faster and completely acceptable, and sometimes the task just is a bigger task than you anticipated.
Bottom line, always communicate (both up and down the chain) if you think a new ask is going to affect other timelines, communicate if something is going to take longer than anticipated, and communicate if you have a faster alternative. So really, just communicate. I totally understand there are companies where CYA or blame-culture makes the idea of being open/honest about things like this is dangerous for your career prospects (at least at that company). To that I just say: consider finding a place that doesn't have so much "office politics", they absolutely exist and they are so much nicer to work at.
I've been lucky to work at some places that are very clear about their asks and also are very open to you coming back and saying "So I looked into this and to do it the way you want it will take 2 weeks or I can get it 90% of the way there in <1hr". Being open to that back-and-forth as well as surfacing the different time estimates are both important and can benefit everyone. It's sometimes hard to know, as an employee, when asked to do something if it's important that it be "pixel perfect"/"exactly to spec" or if it was just an idea someone had who would be happy to settle for an alternative that takes a fraction of the time to complete.
As a manager I've found how important time-boxing certain tasks are and asking people to circle back if it's taking longer or if they later realize the task is bigger than either of us thought. Sometimes we have to take the time and sometimes it's something that we need to think about a lot more before we dive in. The worst is when you get busy with something else then find out the next day that someone spent all day on a task you thought would take <1 hour. Sometimes it's a misunderstanding of what needs to be done, sometimes it's the person trying to match exactly what you asked for even if an alternative would be way faster and completely acceptable, and sometimes the task just is a bigger task than you anticipated.
Bottom line, always communicate (both up and down the chain) if you think a new ask is going to affect other timelines, communicate if something is going to take longer than anticipated, and communicate if you have a faster alternative. So really, just communicate. I totally understand there are companies where CYA or blame-culture makes the idea of being open/honest about things like this is dangerous for your career prospects (at least at that company). To that I just say: consider finding a place that doesn't have so much "office politics", they absolutely exist and they are so much nicer to work at.