Watch the Mixing It Up online guitar lesson by John Goldsby from Upright Bass Handbook
You can make your basslines interesting by mixing things up: use notes from the chord, notes from the scale, or chromatic leading tones. This short, one chorus etude is the same 12-bar blues in Bb that we've been working on.
Once you have this line under your fingers, I encourage you to experiment improvising your own lines using chord tones, scale tones, and chromatic leading tones. Then try writing out your own line and playing it with the playalong track. Look at each bar and analyze whether the notes belong to a scale, and arpeggio, or if they are chromatic approach notes. Sometimes a note can be analyzed as more than one thing (a chord tone also belongs to the scale; a scale tone is sometimes a half step away from a target note).
You can make informed choices using the bass-line concepts we've learned here, but the ultimate guide is your ear; how does your bassline sound to you?