If this is an Android phone, go install Accubattery and do what that says. It's designed for many different phone batteries and associated tech (e.g. overcharge circuitry).
There are so many different models and variations in the electrochemistry, general advice is usually a miss.
If you insist on generalizing lithium tech, keep it between 30-80% charge for good longevity. The extremes of full and empty are rougher on it.