So let's start out this lesson by analyzing how chord shapes work with a low B string.
You'll notice that the basic bar-chord shapes remain the same, but we must avoid the G string (and all strings lower) due to the guitar's natural tuning "flaw" causing the G to be a semitone too high. Some of the chords are still written with a bar across all 7 strings, solely due to the fact that we must avoid them at all costs, and an effective way to "kill" them is to simply bar the entire fret.
Open Position Chord Practice
One of the most popular methods of chord playing on a 7 string is simply incorporating our extended range into chord progressions we may already have come up with. When you can vizualise the notes on the 7th string, you'll find youself coming up with all kinds of cool ways to "beef" up your chords. For instance, a regular open-position D chord? Throw in a third-fret D (on the B string) and hear it come to life!