Studying or practicing Ear Training?  If you're a musician, you should be.  You'll find my Palm software Ear Trainer invaluable.  Also, I teach guitar lessons in Orange County, CA.  (See OCGuitarLessons.com)

 
Once you have the Pitches of the fretboard memorized, the following shapes can be applied by positioning the chord root (which in all the shapes below is the lowest note) upon the intended pitch.  You will recognize the shapes from the core Open Triads.

1.		Know which pitch is the root of the desired chord.  E.g. you may be reading it from a chart, recalling it from memory, or improvising it.
2.		Know what fretboard position you will play the chord in.  This may be a matter of convenience, e.g. where your hand already is; or of convention, e.g. where you know a previous guitarist played it; or a matter of your own preference.
3.		For the fretboard position your hand is in, recall where on the bass strings the root pitch occurs.  This is where the memorization of the fretboard pitches, at least for the bass strings, is essential.  You need to determine if the desired pitch is on the fourth, fifth, or sixth string, and also if that pitch is on the right or left relative to your hand.
4.		Recall which movable chord shape from below applies.
5.		Finger it and play it.  The shapes below are uninverted or in "root position", meaning the lowest note is the root.  Simply position the lowest note on the desired root pitch.

Root Zone	Major 7th	(Major- Minor) 7th*	Minor 7th	Half- Diminished 7th
6 Left a.k.a. E or F Form	or		or	or
6 Right a.k.a. G Form
5 Left a.k.a. A Form				or
5 Right a.k.a. B or C Form	or			or
4 Left a.k.a. D Form