"How to properly charge your li-ion battery and increase battery life?"
This is what I got so far.
1. Battery life cycle: Any Li-Ion battery life is measured based on how many times can you discharge it from 100% to 0%. Normally the figure is 300-500 times and it depends on a factor called DoD (Depth of Discharge).
2. Depth of Discharge (DoD): Quite self-explanatory thing. If you have 20% charge left, it means that DoD=80%. The higher is the DoD the lower is your battery life cycle.
Comparison table is here:
So, here's the answer to the painful question "Why should not I discharge my li-ion to 0%?" The answer is - your battery will die faster. I'm trying to get used to put both my OEM and Mugen Power batteries to charge right after my Nexus informs about 15% charge left.
3. Deep discharge: Not allowed for li-ion batteries. This is pretty interesting: Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to about 3.0V/cell, stopping the current flow. If the discharge continues to about 2.70V/cell or lower, the battery’s protection circuit puts the battery into a sleep mode. This renders the pack unserviceable and a recharge with most chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long storage period.
Also: Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week.
So, what I got from this section is - when I get to 0%, I will not try to switch on my phone again because that can damage my battery.
4. Don't charge in small portions: This is important in a long term for higher capacity batteries. If you use an extended 3000+mah battery it's important to use the whole capacity of the battery to avoid aging of cells that are not used. It's recommended to charge your extended battery to 100% from time to time.
5. Recycle your batteries
I think this article here could be updated a little with these.