A note on battery care (not just laptop batteries): 

Batteries have a maximum number of discharge/recharge cycles built into them. To make a battery last as long as possible try to minimize the number of times you discharge/recharge your battery. Depending on how you use your laptop you can:

• Leave your computer plugged in at all times and only put it in when you are mobile (or every couple months to recharge the cell).
  

• Drain 50-70% of the battery between recharges when appropriate (if you know you're going to have a portable time coming up charge the battery fully before hand)
  

• Keep batteries in a comfortable temperature range. Hot batteries will change their chemistry and die if they don't explode. Do not use the electronics while hot ( greater than 122 degrees fahrenheit or 50 degrees c aka hot to the touch).
  

• If a lithium battery swells remove, and DO NOT charge it. This is now a fire/explosive hazard
  

Also

• A couple times a year you can drain the battery completely to reset the "Estimated runtime" on the computer/device
  

• Recharge the battery every 4-6 months if you never use in that time frame - batteries naturally loose their charge even when not in use.