Videos are a heavy battery usage item. You should consider adjusting the graphics display processor being used.
Multitasking a lot will slow down your machine. If you aren't using Bluetooth, turn it off. Command-Tab will show you open applications. Use only those programs you need. Having an overfilled hard drive (over 85%) will cause the operating system to swap files too much. http://www.apple.com/batteries/
explains more about Apple's Battery usage.
Just dimming the screen and using in an area without too much glaring light can do a lot to save battery life.
Using Airplay can also affect battery usage.
http://www.etrecheck.com/
is a program that can tell us all your background running processes. Some you may have inadvertantly downloaded, and need to be removed. The only process you should even consider running regularly is a backup process.
All system optimization tools are also battery life suckers, and should not be run.