| Jammin jammin
In order to learn about key centers "tonal centers" and be aware of what tune a key is in you should learn about diatonic harmony of the major scale. Since there are 12 major scales, to learn all of them and the harmony within each is the long term goal. For a short term goal, learn about chord types and how each type is built. For example, a major triad is the 1-3-5 of a major scale. Learn major (1-3-5), minor (1-b3-5), diminished (1-b3-b5) and augmented (1-3-#5) triads, as well as 7th chords such as major 7th (1-3-5-7), dominant 7th (1-3-5-b7) and minor 7th (1-b3-5-b7). There are others, but in rock, blues and funk those 7th chords will get you started. Also learn the diatonic harmony formula of a major scale. I-IV and V chords are major, ii-iii and vi are minor and vii is diminished. Eventually learn the diatonic chords in all 12 keys. This should get you started. One of the bass books that talks about all of this in detail is my Beginning electric Bass Book from my Beginning Electric Bass Method series. After studying these chords you can take it further and learn about pentatonic scales, blues scales, the modes and more info.... all of which is in my Intermediate book.
Hope this helps.
Dave | 
