Often one has a rough idea of what needs to get done in the coming week.
From experience, I find that it is best to sit down and plan things out. One should put things down on paper.
It is not so much to remember what needs doing, rather as a reminder of one's priorities each day.
Depending on the level of thought and trouble, only schedule about 3 to 5 major things each day. Life only gives you that much to accomplish each day between interruptions and poor planning by others.