how to create a rocking bass line
I can play enough to jam with people, watching a lot of videos on technique and such (Scott's and Mark's videos), but what I'm not finding is good instruction on practical aspects of creating a bass line. Not talking about improvising necessarily (although I need that too)... but assuming I have time to sit down and plan out the bass line... What exactly to play? I can manage to put together a bass line by combining some linear chord tones and arpeggios etc, and it sounds OK, but I always feel like what I end up with is not what a decent bass player would play. It gets the job done, supports the low end, but lacks character and interest.
So I'd like to find videos with some more practical applied instruction. Like "Here's a medium-tempo Em-Am-D-C guitar progression, and here's how we make it groove on bass." For example, I feel like a common strategy to develop interest in a bass line is to jump across octaves. But when do you do this and why? Or when do you use pentatonics in a bass line and why? Anyone know of a good source for getting that kind of practical knowledge? (What to do when and why.) Thanks.