Also maintain a good thumb position with the left hand. If the thumb is to high then you will feel the "need" to press hard to have all of the notes heard. If you keep the thumb behind the 2nd finger and more in the middle or try lowering the thumb it will give you better leverage to play those chords. Here is a quick tutorial on the topic:

http://www.youtube.com/watch?v=0araEmTbN1w

All the best!

Joe Pinnavaia,
http://www.guitarlessonsbuffalony.com