Watch the 4 Chord Jam Em-Gm-Bbm-Dbm online guitar lesson by Frank Vignola from Vamps, Jams and Improv

This groove is a four chord jam taking minor 7th chords, starting with E minor 7th and moving them up in minor 3rds every 4 or 8 measures, depending if you are in cut time or not (most guitarists read in cut time as opposed to common time).
I utilize two rhythm styles for the two video jam demonstrations. The first is more of a strumming style and the second is more of a spacey legato style using some chorus.
Experiment with effects as they are a great tool for adding textures, sounds and vibe. Practice, practice, practice every day with a pre-determined practice routine. Spend a little time each day with new concepts, new exercises and old concepts to keep them from escaping your vocabulary.