Turn off cortana, turn off "internet explorer" in Backup options. Also set mail to check for updates every 2 hours. Turn off location. Turn off feedback. Turn off wifi sense and other internet related settings.
Mine lasts for about 12 hours now while it earlier lasted for 14 hours but I have Cortana enabled.
Also try this:
1. Completely charge your phone and allow it to drain completely.
2. Don't use it too much for 2 or 3 days (Make sure battery lasts for about 12hours or more)
3. Allow it to discharge to 0% until it switches off. Then charge again.
4. Repeat the cycle for 2 or 3 times. And then start using normally. A lot of improvement in battery.