The rules for handling Li-ion batteries are as follows:
1. Use them--don't store them, as their maximum useful life is four years regardless of what else you do to them.
2. If you must store them, do so at a charge level of 40%.
3. Don't get them too hot, especially when charging or discharging. They absolutely must be kept cool.
4. Use the correct charger. Using a charger for another type of battery will quickly destroy the Li-ion battery and is likely to make it overheat and catch fire/explode (and that's not "likely" as in "there's a theoretical possibility"--it probably will).