J/k about the portrait of tracy thing.
Ok, you have to train your ears. Most of the time, you don't
hear the bass, you
feel it. If you heard it better, we would be noticed a lot more, wouldn't we? But yeah, that's why we have really good ears. We listen. Anyway, try listening to the song while reading the tab. That can help in hearing it. And if you're listening to rock, the bass almost always mirrors the melody guitar. As for tuning your bass, go
here. It should tell you how to tune it, just click the links on the left. Oh, and cyberfretbass.com is a good website for beginners. Hope that helped!
