all i know for battery life, constantly closing my apps properly keeps life, also not always having location services on and keeping it on silent with no vibrate helps. obvious they are though
screen brightness and also since i experienced this issue with 6.1.3 i did the following and it worked for me (listed this on page 3 but ill re list of people havent looked through the post)
go to settings - mail, contacts, calendars
go into icloud mail and turn each switch off one by one making sure you select the save to iphone option not delete
then repeat this on each email account folder
once all are at off ensure all apps are closed and hard reset phone (home and power) this will restart the phone after a few seconds
let it start up and then go back into the same settings and turn each switch back to on
im not sure if it will work for everyone but it worked for me so if youve not tried it, its worth a go, and seems less complicated than deleting all your apps and having wifi and 3g off etc
hope it works for you