Let’s say you have 13 tasks split across 5 clients, where do you start?
I follow (and recommend) a simplified version of David Allan’s Get Things Done (GTD) approach.
In the original version, there are 5 steps to this approach:
Step 1. Capture: Collect what has your attention
Write, record, or gather any and everything into a collection tool.
Step 2: Clarify: Process what it means
Is it actionable?
If so, decide the next action and project (if more than one action is required).
If not, decide to trash it, reference it, or put it on hold.
Step 3: Organize: Put it where it belongs
Place the categorized content in appropriate places, which could be in a task list, calendar or projects folder.
Step 4 Reflect: Review frequently
Review and update daily and weekly to maintain control and focus.
Step 5 Engage: Simply do
Perform the actual task.

To learn more, you can read David Allan’s book or check out this 15 minute video. Note: The picture was taken from the video.
The takeaway
GTD is an effective approach that can be used for both business and personal tasks.