To avoid charging them incorrectly, I invested in a proper charger. I do not have a strong recommendation. Your mileage of "proper" may vary and so may your requirements. For example, I wanted a dual charger with high charging currents, which restricted my choice.
To store them the right way, I always first let my charger charge/discharge the accumulators to half their capacity (give or take) and put them in a safety bag (https://hobbyking.com/en_us/lithium-polymer-charge-pack-18x22cm-sack.html). I only re-charge accumulators to full capacity at most one day before using them and put them to storage mode asap afterwards.
They explode otherwise. Spectacularly. I learned it the hard way. Go check Youtube to learn it the easy way.
So what do I do now?