Another bass tip: bass generally supports the music. In contrast to guitar which generally IS the music. So I think about bass differently. Write your song and record it or whatever, then lay down your bass line to support what you wrote. If you aren't recording, then hear a song in your head and play along to it.
Bass is also good at filling in the gaps. So if you're recording a song do your guitar and vocals and then where there's space, have the bass make it more interesting. But when other things have the focus - usually vocals, sometimes guitar - the bass should be simple and rock-solid.