firstly welcome to ultimate guitar, if you repost this in the bass forum you will get a better response, the new members q&a forum is for new members asking questions about the site
Alexithymia - Anberlin

In The Valley of the Dying Sun - House of Heroes (specilly the bridge)
as a general answer to this question, try to learn the bass lines of the song you allready know or of the songs that you like, youll later start to hear whats more demanding and interesting.
secondly, dont repost this in the bass forum, do a search in that forum you will surely find another thread identical to this one k? Enjoy your low end