Tip: Don't want to keep your phone in silent mode, but can't answer right now? To silence an incoming call, press the volume down key. You can also set your phone to mute the ringing when you pick the phone up: tap Settings > Motion > Mute on pickup.
If you want to be able to quickly reject a call, tap Settings > Motion > Turn over to reject call. When there is an incoming call, turn the phone over to reject the call.