The power consumption for the iPhone / iTouch isn't bad considering its 400mhz processor, and large backlit display.
We have never run out of power in the past year using our iPhones.
We do have mobile and/or AC adapters on hand when we travel, however, and we're not afraid to use them.
Still, there are a few things you can do to preserve battery life...
Keep your device out of direct sunlight, or any hot environment.
This will degrade your battery life significantly. (Ideal temperature is 72℉, 22℃)
Keep updated to the latest software.
Apple is constantly tweaking their software.
(If your device is hacked, check with the online community before updating, however....)
Adjust the backlight display lower than the default of 50%.
Tap 'Settings', tap 'Brightness', and slide to a comfortable level.
Turn off "Push eMail" rely on intervals, rather than instantaneously.
Tap 'Settings', tap 'Mail', select the 'push' account, tap 'Use Push Mail' to Off.
Set eMail retrieval to manual. (or every hour, half-hour?)
Tap 'Settings', tap 'Mail', tap 'Auto-Check', select your interval.
Check fewer eMail accounts.
(Maybe create a free account [ex: gMail], and forward, or have your accounts retrieved by the new one.
Turn off WiFi when you aren't using it.
Tap 'Settings', tap 'Wi-Fi', tap 'Off'.
Turn off Bluetooth when not in use.
Tap 'Settings', tap 'General', tap 'Bluetooth', tap 'Off'.
Set the display screen lock to a short time span.
Tap 'Settings', tap 'General', tap 'Screen Lock'.
Lock your device when through using it.
Press the 'Sleep' button. (The one on top...)
Use Screen Dimmer, if equipped.
The third party app 'Extended Preferences' provides a screen dimmer option, you can set (aside from the screen lock option).
FYI; Placing your finger above the earpiece on the iPhone when waking allows the phone to dim its display. (It then assumes its in a dark room, keeping the backlight dimmer.)
Turn off the music equalizer.
Tap 'Settings', tap 'iPod', tap 'Equalizer', select 'Off'.
When on a call, press the 'Sleep' button (if using a hands-free device) to turn off the display, the call is not effected.
Press and hold the 'Home' button a couple seconds to stop the app when finished.
Some apps use CPU cycles if left running. (Quickly pressing the 'Home' button.)
Battery maintenance:
It is recommended to run the battery down as low as possible about once a month.
