Extend the battery life on your iPhone
Thank you Apple for these tips. I find them very useful now that I own an iPhone.
Optimize Your Settings
Depending on how they are configured, a few features may decrease your iPhone battery life. For example, the frequency with which you retrieve email and the number of email accounts you auto-check can both affect battery life. The tips below apply to an iPhone running iPhone 2.0 or later software and may help extend your battery life.