I'll try to give you an example of what I'm talking about. Suppose the chord progression was G to D, this is one way of doing it using triad shapes and voice leading. The chord tones are in parenthesis (sp?)
G chord: 1st finger, 2nd str., 3rd fret (D), 2nd finger, 3rd str., 4th fret (B), 3rd finger, 4th str., 5th fret (G)
D chord: 2nd finger, 2nd str., 3rd fret (D), 1st finger, 3rd str., 2nd fret (A), 3rd finger, 4th str., 4th fret (F#)
You'll notice you will be able to make this change extremely fast, and it will have a different sound then if you used bar chords or open str. chords, it's called voice leading. Good Luck