Low Octave with Downstrokes
The G major scale is the scale associated with the G major chord and is a great starting place for developing your left hand technique.
For this scale, we're only going to be working with the 3rd and 4th strings. The first note is the lowest note on the mandolin, which is your open 4th string. At this point, just use downstrokes to get the left hand fingering down. Watch the video below for a demonstration.