Since we don't know what you are doing currently, and have no way of knowing whether your battery life is being wasted or is actually as good as you can get from the phone you have in the reception conditions you are in, I think this question cannot be answered.
There are plenty of generic answers: turn the brightness down, stop apps polling for updates every 5 minutes, use WiFi rather than mobile data where available, don't allow it to check nearby WiFi basestations for location purposes even when WiFi is "off", stay away from places with poor mobile signal, don't overheat the phone (not only bad for the battery's longevity, but it will discharge faster), remove any task killers/RAM boosters/battery optimisers/whatever else the snake oil salesmen are calling those things this week. But it may be that none of this applies to you anyway. Without information from you it's hard to say anything useful.