i only refer to tabs as if i'm refering to a practice score, i.e. so that i dont get lost in the song and i know which part comes next (chorus, verse, riff, etc)
listen to the song in parts, slowly. if u're trying to tab metal/power metal/"fast stuff", it'll take abit more patience.
you can download a tab for reference, but if something in the tab sounds different from the song to you, it's probably wrong. don't trust tabs unless they were written by the artist himself!
As with anything else, it'll take some time, as your ear has to get accustomed to the sound. It's kinda like when you first learned how to tune your bass using the fifth fret.
During your first year or so, you'll probably take forever, and it'll still be a little out of tune. As you play more and get more experienced, you'll be able to tune up faster because you're familiar with the sound. You'll also be better able to pick up a string that's out of tune.
For songs, it takes time. important thing is to ensure that you're in the same tuning as the artistes. It'll look really strange to you if you're tuned in natural, and the song you're trying to learn is in Eb (most Guns and Roses songs and some Matchbox 20 songs are tuned a semitone down)
If you get stuck, it's good to check some tabs for a rough reference. Alternatively, you can go to somebody more experienced to ask for help.
Don't worry dude, it'll take some time. Be patient, only fools rush in.