Watch the From The iii: Over Minor online guitar lesson by Rob Garland from The Guitarist's Pentathlon
By playing Am pentatonic against a Gm7 chord I'm able to play tones such as the 6th and 9th that are not normally available to me in the minor pentatonic scale. I focused on these notes in the licks I played and let the notes hang over the chord. Once you get comfortable with the sound of the scale against the chord try playing all five shapes of Am pentatonic. The pentatonic notes you are used to hearing will sound different because you are playing off of a different root note, which is a nice change for the ear.