Time is our most valuable asset. The homeless man and Bill Gates both have 24 hours a day. Another tip I have found useful for me is to do the least desirable task first thing in the morning. It gets the task out of the way and begins the day with a feeling of accomplishment and encouragement, rather than full of dread at the very thought of having to do the task.
Also, I've learned to leave room for unexpected surprises. If I plan my schedule on a razor's edge, I am setting myself up for failure, because most things don't go exactly as planned.