iPhone Battery on 6s

Hi there! I recently switched from droid to iPhone and I have a 6s. It is older, but it was given to me free by my coworker. The battery seems to die fast. Does anyone know any good tips to keep the battery life up?

Thanks!

Yeah, i know how to life up. The most important, is to switch your internet off as long as it can be.

get a new battery, you can check the life of the battery on settings