when you have notes in the bass and the treble clef how do you determine the chords? should I look only at the treble clef to determine the type of triad or 7th and look at the bass clef as just an accompanying bass note? if the treble clef only has two notes, do I use the bass note then to make a triad?
You must take all notes into consideration. The song could be arranged in different ways, with chords in the treble cleff and bass in the bass cleff, or arpeggios that go from the bass cleff all the way to the treble cleff, for example.
So if you have CEGB in the bass cleff and EGB in the treble, it would be inaccurate to look at the treble cleff and say it's a Em, because that C on the bass makes it clearly a Cmaj7, right? All notes matter.
If you have the melody in the treble and also the bass, then that is already a good indication of the harmony. Of course there would still be various possibilities, and it is up to you to choose what works best for you. The bass line is more likely to indicate your harmony as the melody could be harmonized in almost endless ways. Look at the combination and see what it suggests and what suits the piece best.
There are two answers to this.
If you want to analyse the harmony, all the notes matter. In fact, the bass note probably matters more than any of the others!
But if you're a guitarist wanting to know what shapes to play, and there will also be a bass player in the band, it can be useful to look at just the treble clef. To take @coconochao's example, EGB in the treble, C in the bass. Yes, overall it's Cmaj7. But the composer/arranger didn't put all four notes in the upper part, and maybe you shouldn't either. You play EGB, leave C to the bass player. Whether you think of this as 'I play Em' or as 'I play Cmaj7 but omit the root note' doesn't make any practical difference.