1) try different fingerings of the chords. Any given chord can be played a million different ways
2)make sure you're warmed up first. I have really, really thin fingers, and blood circulation issues. That means that during the winter, I HAVE to play in a warm room and spend half an hour warming up. Cold fingers = choppy playing.
3) when you practice the chords, do them SLOWLY. Ignore the rhythm of the song. Focus on making the chord changes correctly, and on your own time. Then start building up the speed of your chord changes. In fact, you can even use a metronome. Pick a comfortable speed, and change your chord every four beats. Then slowly build up your speed. Make sure you get a clean sound each time. Trust me, it's easier to do it murderously slow and get it right, than to do it fast and have to unlearn mistakes.
Break it up into 10-15 minute bits. Practice the chord changes for 10-15 minutes, then move onto something else. Come back to the chord changes a little bit later. You'll have them down like silk in no time. :)
My biggest challenge to date has been this chord change:
Am7 -> Bm7 b5 -> Em7 b5
From the song "Black Orpheus." I spent a good week learning that chord change. :P
Oh, and another little cheater's trick: Sometimes if you throw in a little bass line from one chord to another, it gives you a chance to get all your fingers in place. Try doing a chromatic walkdown from the bass note of one chord to another to get you in place.
One big example is
