This is a good rhythm guitar exercise – it’s focused on getting you really smooth at changing between different chords. It can also help train your ear – you learn how different chords sound together.

First, create a bunch of flash cards with different chords on them. The more the merrier. Bonus points for not just naming the chords, but for putting the fingering on it – that way you can have the same chord several times, but with different fingerings.

(Click on any of the images to see them much bigger in a new window)

Here’s a pile of these flashcards that I made on the backs of blank matchbooks:

Next, dump all the flashcards in a bag or a hat or something:

Start pulling flashcards out. The first one you pull out goes on the top row, then the rest of them in the row below:

The exercise is to play through these, going from the chord on the top row to the first one in the second row, then back to the top row, then to the second one in the second row, then back to the top row, etc. So, using the layout pictured above, the chord pattern I would play would be:
Cadd9 – E11 – Cadd9 – B7 – Cadd9 – G13#9 – Cadd9 – D7sus4/A – Cadd 9

This may not sound all that fabulous, but after you finish, you will never have trouble going from that Cadd9 chord to any of those other chords.  Eventually, you should be fluid enough that you can flow from any chord to any chord.

As far as the rhythm goes, I’d suggest starting with a very simple pattern – downstrokes quarter notes in 4/4, changing each new measure. Then make your strumming patterns more complex, but never lose the groove. Keep the following in mind as you do this:

• Timing is everything – use a metronome or a drum machine, and learn to be rocksteady as you go through the changes
• Focus on making the transitions as smooth as possible
• Make sure that each note in each chord is clear
• Don’t speed up until you can do all of the above
• If you discover some cool chord progression while doing this, write it down and use it in a song!

Bonus points if you record some of these random progressions, and then practice soloing over them. This can help you learn to play over crazy changes, and can also help you find interesting melodic ideas that you might not have found otherwise.  If it sounds terrible, well, do the exercise, then move on with your life.