In either Rookie DJing, Pro DJing, or Master DJing mode, pass all 4 songs with an average of 95% or higher (A+), and you will get to play CnP as an extra stage while the credits play. This is the only way to play this song, as you cannot unlock it.
To unlock the following songs, you must accumulate the indicated amount of MAX. MAX is gained by simply playing songs. To see how much MAX you gained after a song, look in the bottom right corner of the results screen. To gain more MAX per song, use a different NOTE from the gear screen.
Next to the unlockable will be, in parentheses, an indicator as to what the unlockable is (a song, note, gear, course, OST)
In order to unlock the following items, you must be in Freestyle Mode (this mode carries combos over from song to song). When you get over the specified combo amount for an unlock, you must break your combo. You will then unlock the next item on the list that you haven't unlocked yet. Also, there are images unlocked in intervals of 500 up to 19,000. It is unclear what exactly these are, and there are too many of them, so I am not listing them.
These will take forever to unlock, so I suggest you download the 100% Game Save that is on here...