Need help figuring out chords in a song
The basic approach to learning any song on guitar is to begin by determining the bass notes on the lower strings. Those will generally tell you what key the song is in. Most popular songs have three or four basic chords to them, so finding the root note will tell you what chords to use.
Take for example, a song that has the following structure: Am - C - D - F. You'll find the A and the C on the fifth (A) string, and the D on the fourth and F on either the first or fourth. Once you've determined the root notes, you can then further determine the mode of the chord. A major doesn't sound right for the first, so then try minor, seventh, etc. Your ear should help you in this, and you're helping your ear in the same way.
Duke Ellington said it best: "If it sounds good, it IS good!"