Although there are many options for harmonizing minor key melodies, there are certain chord choices which are more common than others. The most common II V I progression in a minor key is made up of a IIm7b5, aV7 and a Im7. The I comes from the natural minor, the V comes from the harmonic minor and the II can be created from either scale. Here are two minor key II V I progressions with chord arpeggios, followed by improvised lines played over the progressions using the chord tones.
Another common practice in minor keys is to use a minor triad as the i chord with a line of guide tones either above, below, or running through the chord voicing, resulting in various changes to the overall chord. In the following example, notice that only the upper guide tones are needed to create the various G minor chords.
This example uses the above guide tone line and extends it to include all the chords. Analyze the line against the chords and then transpose it to all the other keys.