How to make iphone 4 battery last longer?

I'm going to California tomorrow and I'm driving. It's about a 6 hour drive from where I'm at. I want my phone to last but my phone's battery does very quickly. I already have all the notifications shut down along with the location services. Also the screen is dimmed down some too. Any suggestions?

Car charger? New battery?

Turn Wi-Fi, GPS, Bluetooth and Mobile Data off. Try going to Airplane Mode which will not allow any calls and text messages to reach you and will save your battery drastically. Turn off the sounds and vibrations it will also help.