IPhone 5S Battery (Lithium-Ion)?

When you get a new one, is it best to let it die completely and then charge it all the way, or should you charge it once you get it?

I believe iPhone's use a Lithium-Ion battery?

Li-Ion batteries like to be fully charged. About once a month, let it run down under 20%, otherwise try and keep it charged when you are not using it and it will last longer.

Yes they do. I always leave mine until its on the very last percent then i charge it. If im constantly. On it it lasts 2 hours if im just on it to quickly chexk the time or facebook every ten minutes it lasts all day x