To palm mute properly you must first have proper pick hand positioning.
Hold your picking hand with the side that runs along your 4th finger parallel with the bridge of your guitar and as close to the guitar as possible. This will allow you to use the side of your hand or the palm to mute and control your sound. Try different ways of muting by rocking your hand; find a comfortable spot where you will have good control. I use the part of my palm that connects to the thumb and the side or the part of the palm that runs along with the 4th finger. Both give me a different sound and effect.
Many bands use muting and muffling to create a unique sound for the guitars and this has a big effect on the overall sound of the band. Try muting then hitting notes full sound back and forth to get the hang of the technique until it starts to become part of your own sound!!!
Hope this helps
Yours in Music
John McCarthy is the co-owner of The Rock House Method and a leading inovator in the field of video lessons for musical instruments such as guitar, bass, keyboards, drums and vocals.