guitar and bass

hello all,
i was wondering:
if a guitar plays a chord like a E chord or Gchord
what do i need to play as bassplayer to play along?
do i just play a E note or G note?
is that all :O?!

Well, the note of the same name is always a good start but of it's a major chord, and "normal" E or G chords are, you can play any note in the major scale with the same name (and even some that aren't in those scales, if you really want to). But it's best to just start on The E or G and experiment with different notes around those till you find something that sounds good.

Play any note in the chord. Music generally sounds at its strongest when you build it around chords rather than scales. For example, if the guitarist plays an E Major chord for one bar, play something using the notes E, G#/Ab and B.

studybass.com can explain all this far better than I can

http://www.studybass.com/lessons/bass-chord-patterns/about-bass-chord-patterns/