well you HAVE to use wifi on any 4g device when you can, or toggle off the 4g and use 3g if battery life is a priority and you aren't going to be near a charger all day.
Personally, i just use wifi when im at home and at school, 4g whenever i'm not (live in NY so it's a good 4g signal pretty much everywhere).
Also keep my brightness on auto - saves alot more battery than you might think.
And the 4.65 inch screen is a huge drain, for sure. Battery life...