I keep my 4G data off all the time unless I need to check email or something and I'm not near wifi. Same goes for wifi, when not near a wifi source, I keep it off (I have an app that automatically turns off WiFi when out of range because WiFi constantly searching for a signal is a battery HOG) but when near wifi, it's on most of the time. This behavior started as a way to save data since I started out with a limited data plan and then it just became habit. Now I get 5GB a month with roll over which usually means I get over 9 GB a month to use. Not an issue about saving data any more but my habit is a great way to save battery, so that's the main reason I continue to use my phone in this manner.
Brightness is on auto and I have it trained to be a little on the dimmer side.
I've been doing all of the above things on all my phones for the last 7 years or so.