Assuming that you both have Cakewalk or Sonar installed on your machines, the simplest way would be to burn a .bun file onto CD (of course. this also assumes you have a burner). You can then reload the .bun onto your friend's computer for use.
If you are using two different recording programs, it becomes a little more difficult. In that case you will probably have to save each track to a seperate .wav file and then burn the individual waves onto CD and import them into his recording program.