battery drainers
There are no astral bugs/facehuggers leeching your battery empty! Here are the most common battery drainers listed:

- display
  It's the number one drainer in any battery-powered system.
  The brighter, the worse.
- mobile data
  Transmitting and receiving data wirelessly needs a huge amount of power, too.
  Due to design, 3G (UMTS, HSPA, etc.) drain the battery faster than 2G.
  Disabling data transfer in the background greatly helps improving the phone's runtime.
- wifi
  Just as mobile data transfer, wifi virtually eats battery life.
  Having wifi enabled, your phone *always* scans for active wifi nearby. Go figure how good this is for your runtime.
  Better disable it completely, when you're not using it. There are good widgets for that task. ;)
- bluetooth
  Take a look at "mobile data" and "wifi" and go figure..
- the CPU itself
  Power usage of the CPU depends on the used governor, its parameters and the CPU frequency
  To optimize this, you have just downloaded/installed CPU tuner. :)