Simple and fairly short answer
Never let the voltage of any cell go over 4.2 volts or under 3.0 volts. Using a proper charger and a low voltage cutoff in the car shuld take care of 90% of that. Do not discharge LiPo's, store them in a mid charge state. The exact point is not a big deal, just somewhere around 3.7 volts per cell is good. This way they will not exceed the safe limits if the temperature changes.
Finer points, use a balancer when charging, or even better, a balance type charger. The reason for balancing is to get all the cells to the came voltage, usually 4.2 per cell at the end of the charge. If the cells are not perfectly matched, and they rarely are, they will go out of balance as they discharge. For this reason, I like to set the LVC in the car abit higher than 3.0 volts per cell. I go to 3.3 or 3.4 to allow for some imbalance so the lowest cells at the end of a run is still over 3.0 volts. If you run to the LVC, it is a good idea to charger it part way up before storing it.
I also don't like charging any faster than 1C. Sme cells and packs are rated for more, but the faster you charge, the harder it is to keep the cells in balance.
Hope that helps.