Reddit mentions of Music in Theory and Practice Vol 1 w/ Anthology CD

Start off with music theory, along with playing another instrument (piano, guitar, horns work, too). I personally wouldn't have the attention to learn it on the computer, as I would probably stray off to reddit every couple of minutes.

I would say get a good book. I'm currently learning out of this book which is outstanding. Some people will tell you that learning music theory is "cheating." Those people are called "lazy." All learning music theory does is take the guess work out of music composition, and among other things, gives you a greater appreciation for music.

I guess I should have phrased that a little better - probably the best theory book you can get if you want a thorough but basic understanding of all the fundamentals of music theory would be a college theory text. If you want to just focus in on one specific area like say counterpoint, then you'd be better off purchasing a book dedicated to that one topic. First learn the fundamental theory though. If you get a book focusing on counterpoint, but haven't learned the fundamentals of theory yet, you might have trouble following it or at least not get the full benefit of it.

The book I used in college was Music in Theory & Practice . There are two volumes and optional workbooks for each volume. If your doing the self-study thing the workbooks would be pretty good to get as well. I used the 6th edition, the most current edition is 9th, and I linked the 7th because that one you can still easily find for purchase, and you can get it dirt cheap if you buy a used copy.