Neil,

You should have little trouble figuring out what notes are in most major and minor chords. If you write out a diatonic scale for the root key and continue for a couple of ocatves, a chord is simply every second note. 1-3-5 is the major (or minor) triad and you keep adding the seventh, ninth, eleventh, etc. notes in the sequence. To put it on the guitar just arrange the notes so it's possible to make the chord and drop the ones you can't reach. Occasionally, even the tonic note is dropped. And don't change what you call the chord just because you aren't sounding all the notes it theoretically contains.

Good luck,

- Mark