I don't like the idea of spending 15 minutes on each area, I tried and I spent an hour just on one thing. It could be that I'm a slow learner or that I get absorbed in it and carry on going. Learning to read music is the key to alot of areas. firstly theres the obvious learning to read standard notation, which then forces you to learn the keycentre of a song. Once you know that and you have your hand resting on the fretboard all those scale drills you did when you first picked up the bass just seem to come alive under your fingers. It just made sense to me. The tricky part about standard notation is not the actual notes but the phrasing and timing, well for me anyway.
Chords are important to learn, if you learn chords then you can start to disect songs, my learning is still ongoing on this one but Ed Friedlands walking bass lines helped me.
With regards to technique, if you've been playing a while and whatever your doing is working then just leave it at that. If its tapping or slapping you're after then just buy abook/or DVD for this one. Chances are if you went to a bass teacher they will refuse to teach you that stuff until you've mastered everything else (mine did). For Bass try Ed Friedlands Slap it, and I also use this you tube channel to learn some riffs:
[url="http://www.youtube.com/watch?v=CXfS3HYSiZo"]http://www.youtube.com/watch?v=CXfS3HYSiZo[/url]
Good luck