Take my suggestions friends --- I am getting "BANG BANG" 34 hours battery life on iPhone 4 with iOS 6.
1) TURN OFF ALL LOCATION SERVICES EXCEPT MAPS APPS.
2) STOP THE EMAIL PUSH SERVICE.
3) DISABLE Wi-Fi AND BLUETOOTH (( I don't use wi-fi during mobile condition).
4) SWITCH OFF THE TIME ZONE UPDATES.
5) SET DISPLAY ON ‘AUTO BRIGHTNESS'.
6) TURN OF THE EQUALIZER.
7) SET AUTO-LOCK TIMER TO 1 MINUTE.
8) KILL BACKGROUND APPS WHICH YOU ARE NOT USING.
9) TURN OFF VIBRATION.
10) DISABLE THE DIAGNOSTICS AND USES.
11) TURN OFF 3G WHEN YOU ARE NOT SURFING. THEN USE 2G OR EDGE CONNECTION ONLY FOR RECEIVING PUSS NOTIFICATIONS.
12) KEEP YOUR IPHONE COOL AS MUCH YOU CAN.
13) UNSTABLE MOBILE SIGNAL HURM BATTERY LIFE HUGELY.
14) PLEASE DON'T LEAVE AN APPS PAUSE AND YOU TURN OFF THE LOCK SCREEN AND JUST FORGOT TO CLOSE IT.
USE "SIRI" LESS OFTEN FOR 4S USERS.