There are a couple of post around here on locking the phone versus putting the phone on standby while in your pocket. Most people prefer to put the phone on standby by just pressing the mute button on top of the phone. ( button on top beneath the flashing LED)
Another reason to use the "Standby" option is that it saves battery power... and that's always a nice bonus. You are still notified of calls, texts, emails, etc. Just a thought...
I have made the button on the left side my keyboard lock. That way it is a one button push and I can drop it in my pocket in case I don't have my holster with me.