Mine is a Li-ion battery (I assume yours to be too), so I don't need to completely discharge or do stuff like that, which some people do for old batteries.
I do certain things to take care of this thing:
I think there's this setting in BIOS which enables us to control whether battery is charged more or not after it's fully charged... My battery doesn't charge once it's full, and the laptop starts running on AC power without charging battery once it's a 100%. I don't leave my laptop charged and unattended, but if I do so, I take care that it's switched on so that the BIOS setting uses the power to keep it switched on rather than using it to charge the battery already charged.
If I have to use laptop on battery, I do number of things like decreasing LCD brightness, killing extra processes and useless graphics, turning off networking, wireless, changing graphic card power scheme, giving proper ventilation to laptop while putting cooling policy at passive level, and spinning down hard disk when possible (all these are settings available in the OS you run).
I also defragment the HDD once in a while because HDD is big thing when it comes to power consumption and fragmentation means more reads, and lesser battery life while decreasing HDD life on the other side...
This pie chart shows what takes up how much power:
I also put that CPU frequency to 'powersave' if I am on Linux...
- There are these software like Laptop battery doubler which make your battery last longer if you are on Windows. I don't know its Freeware or Opensource counterpart yet.