Don't allow full discharge. Li-ion batteries don't have a so called memory effect, so you need to charge them often not waiting for them to drain to 0%. The average lifetime of a li-ion battery is calculated in full discharge cycles and is 400-600 full discharge cycles for high-quality batteries. The more often you charge your phone, then longer will your battery serve you.
Fully discharge once in 3 months. Due to a very hectic and unstable discharge process (just think about it - all those apps you run, the unpredictable connections via USB or BT and Wifi, NFC etc etc) it is highly recommended to full discharge your battery once in 3 months and then make a 100% saturation charge (keep the phone on charge for 2-3 hours after it reaches 100%) to reset the charge flags in the battery.
Store your li-ion batteries partially charged. Li-ion batteries loose charge over time and if you store them, it's recommended to charge them up to 30-50% and store at 15°C (59°F) to achieve lowest permanent capacity loss.
Use the original charger at all times. Not many people know that the charging device is actually inbuilt into the phone and the charger that you are using is simply used to reduce the domestic voltage and to rectify current, thus not affecting the battery directly, however some devices don't have an inbuilt charger in them and in such cases using an third-party charger can be harmful for both the device and the battery.
Don't allow overheating and super-cooling when charging The discharge temperatures are from -30°C(-22°F) to +60°C(+140°F), however when you charge your battery, it is highly recommended to do it when you are in +10°C(+50°F) to +30°C(+86°F) temperature range.
