I don't have a sophisticated cellphone, but my battery had to be recharged daily, instead of weekly. They told me to take the battery out for half an hour and then put it back in. It has worked fine ever since!
Make sure you keep your GPS and wifi disabled if your not using it. Akso check running apps for any non 'crapware' (default sw your phone came out with) that is perminantly running and remove it. All in all if you get a full day you should be happy (Thinking big screen phone like S2/S3)