The core purpose of what you do is the one thing that need not change.
One of the most useful tools I've ever learned for time management is the priority index. The Priority Index is a visualization to help you choose what to work on and when to work on it.
The Priority Index places your work on a graph. On the left of the graph, you will have the level of impact from least to greatest. On the bottom you will have the amount of time required to complete the task. It should look like this.
You may notice there are no numbers on this graph. I left this graph simple and blank as the scope of time you're looking at may be different than mine. I sometimes use this graph to schedule my daily activities as well as my quarterly or annual goals.
The next step is to add the tasks on your to-do list to the graph. This does not have to be an exact placement on either impact or time (compared to a Gantt chart which requires accuracy). Instead, your focus should be on keeping all of your tasks relative to each other. At this point, it should look something like this.
The final step is to turn this chart into quadrants. As you'll see in the final version below, the activities will fall under four groups.
The first group are the activities that you can do really quickly and see a high return from your efforts. These should generally be done first. Typically speaking, these are the events I will work on when I have a few free minutes in between meetings. I don't need to budget specific time to work on them, I just need to do them as soon as I can.
The second category are the actions that also have a high impact but take a long time to execute. These are the actions that you need to set time aside to do. These are often the actions that require you to schedule time to focus on them and to make sure they do not fall off your plate.
The third category are actions that do not have a high return, but also don't take very long to accomplish. These are the lower priorities that you'll "get around" to doing at some point. As long as you track them and get to them at some point, you'll be fine.
The final category are the actions that take a long time and also do not have a high return. These are the actions that you need to think critically on whether or not you actually need to do them. Often I will find myself removing these items from my to-do list. If you're a manager, these may be the activities you'll want to delegate, as they may still be a growth opportunity for your employees. Either way, you should honestly assess if these activities are even worth doing.
As a side note, many of you may not have control over whether or not you need to accomplish a task. If you are being assigned work in this category, I will remind you that the consequences of not completing a task should be considered when deciding on it's impact. You may also be able to ask your manager to analyze the value of your time vs the impact of this action and see if they remove it from your workload. At a minimum, you should be able to negotiate the expectation on how quickly you need to do these tasks.
Breaking Down Each Quadrant
While most of us will be able to use this graph to manage our workflow, you may find yourself in a position where a quadrant has many items. If one quadrant has significantly more items than the other three, then you should first ask yourself if you've been honest with your predictions. It is easy to slide into the habit of thinking everything has a high impact and it is difficult to give an accurate prediction of how much time it will take to perform an action.
If you simply have a lot of tasks across the board and need to do a secondary analysis to sort the actions in each quadrant, then you will need to partner this tool with others. For actions that require a lot of time and effort, you'll likely need to manage your bottle necks. For example, you'll most likely be scheduling this work around time and resources. For actions that require less time but there are too many to do immediately, then using the Getting Things Done (GTD) method by David Allen may be your best solution to dedicating time to work on them. This method may also be beneficial in breaking down your actions with a high requirement of time into smaller tasks that can then be scheduled with more flexibility.