Using The Pivot Finger
Can you see how in the example below the first finger stays on the same string all the time, try not to lift it when changing frets just slide it. Once you can do these changes fluently we introduce strumming.

= Strum Down (from the thick string to the thin)
Try and strum along with the example below. Count the beat when you are strumming, this is to help you keep in time. If possible try to tap you foot on every beat.
Another tip is to start changing to the next chord as soon as you've done the second strum. Try to keep the strumming fluent and in time.
