Many people think that even if they don't use a phone for longer time, they should charge their batteries every night. But this could reduce your battery life. You should know which battery type needs how much charging, while purchasing a battery do not forget to ask the vendor.
And try to use original batteries, as they last long.
Most phones indicates if the battery is low, that time do not use your phone till the battery goes off, charge it as soon as possible.
thanks Ramadan. I used to charge my battery everyday night. henceforth i will not do that. I have read somewhere that if your battery does not require charging, then the chargers stop charging it. So i believe there is no possiblity of overcharging?