The most important thing to do when you are trying to keep your mail organized is to make sure you go through it every day so that you don’t have piles all over the place. Go through it and throw away any junk, and sort out the mail that just needs to be filed away.
Buy yourself an easy, and stackable, mail tray. Two to three shelves should be fine. On the bottom shelf put bills and statements that need to be paid right away, or dealt with in some way, such as a phone call. Keep only the most current here. When a new one comes in, take the old one out of the pile and file it away. Then use the next shelf for items that you need to have accessible throughout the year for one reason or another. Not more junk mail, but things like: a phone list for work or school, insurance booklets, car insurance information, mailing labels, or extra birthday/anniversary/holiday cards that need to be mailed periodically. This keeps things all in one place and readily accessible for when you need it.
Now, if you have children, this is where the third shelf will come in handy. Use the top shelf (if its in an easy to reach place) for school notes, lunch money, permission slips, homework, or things that need to be signed and/or delivered. This will be the place for the kids to put stuff for you, but also the place for you to return it to upon completion for them to pick up. Saves having to hunt all over the house or bedrooms for that elusive field trip form!