Getting a head start.

My general advice for those who want to learn the craft--and this will sound cliche--is to start at the beginning.  This is known as theory.  Most harmony books cover basics first(meter, intervals, etc). But I think, it is best to jump start on those topics by either learning an instrument or self-study.  Each of their benefits.  When I learned theory, it was through my piano lessons.  Teachers either use Alfred or Faber or Faber. Both have theory work book.  The theory workbook expands on lessons and provides exercise to train you.  So let us say you were learning about 3/4 in a lesson.  The theory book would go more in depth and other books that cover aspect of the lesson. 

The second option is self taught. Alfred has music theory book: Alfred's Essentials of Music Theory: A Complete Self-Study Course for All Musicians (Book & 2 CDs): Surmani, Andrew, Surmani, Karen Farnum, Manus, Morton: 0038081232973: Amazon.com: Books

Getting ahead of start on this place you ahead of the class. You can probably skip the chapters on theory and go to next part...counterpoint. 

For me, Theory workbook only works after you have some of the Masterpieces in your mind already. I have to know the soul of the works first before trying to learn their craft. Otherwise it's just meaningless to learn the craft and it's better to not compose anything at all.