Compile your to-do list for tomorrow no later than this evening.

I just asked him to do one simple thing consistently without fail. 

At least three times per day at scheduled times, he had to ask himself the following question: Am I being productive or just active? Charney captured the essence of this with less-abstract wording: Am I inventing things to do to avoid the important?

 Learn to ask, “If this is the only thing I accomplish today, will I be satisfied with my day?”

Compile your to-do list for tomorrow no later than this evening. I don’t recommend using Outlook or computerized to-do lists, because it is possible to add an infinite number of items. I use a standard piece of paper folded in half three times, which fits perfectly in the pocket and limits you to noting only a few items. There should never be more than two mission-critical items to complete each day. Never. It just isn’t necessary if they’re actually high-impact. If you are stuck trying to decide between multiple items that all seem crucial, as happens to all of us, look at each in turn and ask yourself, If this is the only thing I accomplish today, will I be satisfied with my day?

The 4-Hour Workweek, Expanded and Updated: Expanded and Updated, With Over 100 New Pages of Cutting-Edge Content. by Timothy Ferriss