Here are my guidlines
-Always charge at 1c (ex. 3200 Li-Po charge 3.2amps or 4800 charge at 4.8amps)
-whenever you feel your battery start to loose any power, pull it off teh track and cahrge it soon as possible(this should be around 6 volts.) You can buy a Li-Po cutoff.
-always use a Li-Po charger, The best all-around charger is the Duratrax ICE
Promarch 4200's, Orion carbon 3200
Novak GTB 13.5