Changing chords is something a lot of beginners struggle with. I have me theories that beginners tend to try and change chords too quickly while they’re learning. By this I don’t mean physcially too fast but rather too soon.
In order to be efficient at changing chords, especially while strumming, you need to first be profeccient in playing and strumming the chord on it’s own. I’m a big believer in breaking down skills on the guitar into baby steps then piecing all those steps together to create the full picture, so lets do that with chord changes.
As I already mentioned you need to be able to make the chord shapes and strum them well before you can think about moving between them. Once you’ve got that down I want you to take the strumming part out of the equation.
Let’s say you’re trying to switch from C to G. Stop strumming and just practice moving your hands from the C shape to the G shape back to the C shape etc. The movement is the same whether your strumming or not but by stopping strumming you’re allowing your brain to focus just on the chord change and manuvering your fretting hand. Once you feel comfortable with it add a straight strumming up down up down up etc. To the mix.
A couple of points to note, if you stumble switching the chord shapes don’t worry just keep on strumming. If you continue to strum steady you’ll get in the habit of being able to leave your strumming hand on auto pilot and worry about moving your fretting fingers around.
Last but not least don’t try to learn too many changes at once. Focus on one chord to one other chord at a time. Then worry about creating chord progressions you change between. Breaking the technique down almost always works for new skills on the guitar and if your patient it will work for you really well.
Other Posts:
http://guitarlessonreview.net/669/learning-the-guitar-fretboard-notes/
http://www.youguitarist.net/291/how-you-can-benefit-from-the-caged-guitar-system/