Fills, fancy techniques, and bass pyrotechnics are all well and good but, really, a great bassline does nothing more than enhance a song. There's no better teacher than Sting...
Listen to the following tracks and marvel at Sting's part playing. No notes are wasted and every note is designed to enhance the music and not show off.
Make sure to subscribe to the newsletter (scroll down) for notifications of my free weekly bass lessons. I'll also send you the Bass Guitar Resources ebook for free.