When mail comes into the house it generally fits into three categories: bills, sales pitches and personal correspondence.  To keep mail organized and be sure bills are paid on time, you can set up a five slot, desk or counter-top filing system that will keep things organized by what week they need to be addressed.  The fifth slot is for anything that is to be paid the following month.  So if your car payment is due the first week, put it in the first slot of your file and then you'll be free to move on to other matters.