The best way to use a day is to lose track of time and take full advantage of the moments that come your way. So many people spend their lives in the future - what they will do and where they will be - but they miss the present, the now. In this moment is all the time they need, all the time they will ever have. Miss that now, and you'd better get used to missing a lot of the future too.
And if that future is to be a good one, it must be based not on materialism, but on spirituality.
Eat healthy every day.
Do sports every day.
Find a community and serve.