I talked to an Apple Genius recently about improving notebook battery life.
His recommendations to improve notebook battery life were:
- kill any runaway programs
- reduce screen brightness to 50% or less
- move any Desktop files you don’t need on the Desktop to another folder. This reduces the amount of screen redraw work.
- update to the latest SMC firmware
- once a month, unplug the power adapter and run your notebook until it sleeps automatically. Then plug in the adapter and allow it to charge for 8 hours.
- if there’s still a problem, drop by an Apple store and he’ll run the battery diagnostics program from their bootable service iPod nano. Bring along your receipt in case there’s a problem still covered under warranty.
Reducing the screen brightness from max to 50% immediately improved battery life on my old notebook by 50%, from about 2:15 to 3:30.
Also, remove the plastic packaging from new batteries to prevent them from permananently sticking to the plastic battery casing. The plastic is sticky on one side and can be cut into several cell phone display protectors. 
apple.com: Apple Notebook Battery Care
apple.com: Lithium-Ion Battery Care
support.apple.com: Apple Portables: Tips for maximizing your battery charge
gizmodo.com: How To Maximize Your iPhone 3G’s Questionably Adequate Battery Life
theappleblog.com: What’s the Ideal Strategy to Maximize Notebook Battery Lifespan?
