Early in the morning, preferably right after you wake up, attack the biggest task you have on your to-do list. Assuming that it can be done first thing in the morning, throw everything you've got into knocking out that big task. This will EXPLODE your productivity because, if you are like most people, you normally spend the whole day skirting the big stuff and procrastinating. Stuff that should have taken a day to finish can drag on for days if not weeks.
Do yourself a big favor and KNOCK OUT that one big thing... first thing in the morning.