Here is a picture of my iTunes Playlists. As you can see I have a very detailed list of Smart Playlists. I recommend that you create folders in iTunes and then import my Smart Playlists.
Fresh Ensures that last played is not in the past 2 weeks.
Highest Rated Allows for 4 or 5 star rated songs to be played more often.
Latest Additions Plays recently added songs more often yet not too much.
Not Often Played Will force less often played songs to be played.