Prevent the Memory Effect - Keep the battery healthy by fully charging and then fully discharging it at least once every two to three weeks. Exceptions to the rule are Li-Ion batteries, which do not suffer from the memory effect. Do not leave the battery dormant for long periods of time.
Always use a battery charger, which is by the same manufacturer as your phone, it gives it more life. It also helps if you overcharge your battery now and then.
Keep the Batteries Clean - It's a good idea to clean dirty battery contacts with a cotton swab and alcohol. This helps maintain a good connection between the battery and the portable device.
Do not leave your cell phone near any source of heat, a common place ...