Although, you may not get even close to these numbers, but I will attempt to provide all tweaks and settings to get as close as possible. I have collected most of these tips from Apple's fine prints and some from support page of an iPod. Don't worry, I am not going to ask you to turn of Wi-Fi or other features that would simply cripple your iPhone.
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Brightness setting: this alone
can do the trick of getting most out your iPhone's (or any device for that
matter) battery life. Even though iPhone has bright and gorgeous
screen, you may want to turn it down to get that screen playable little
longer!
How-to: "Settings" -> "Brightness" -> slide it to about one seventh -
Auto brightness: iPhone has built-in
sensor that checks the lighting condition where ever you are and adjust the
brightness accordingly. This is sweet feature, but the sensor eats up
battery life.
How-to: "Settings" -> "Brightness" -> turn the "Auto-Brightness" switch "OFF" -
Auto-Lock: turn that display off as
frequently as possible. Make sure it is set to 1 Minute
How-to: "Settings" -> "General" -> "Auto-Lock" -> "1 Minute" -
Auto detect Wi-Fi: iPhone has feature
to
How-to: "Settings" -> "Wi-Fi" -> "Ask to Join Networks" -> turn "OFF" -
Email Check frequency: this may not be
suitable for lots of business or frequent email users, but it does save
battery life. You can set iPhone to check email every 15, 30, 60
minutes or do manual check. Of course, ideal setting for saving
battery would be "Manual", but you can also set to "Every hour"
How-to: "Settings" -> "Mail" -> "Auto-Check" -> select "Manual" or "Every hour" -
Turn of some sounds: iPhone makes
noise for about everything you do on it. You can turn off some of
these sound effects such as keyboard click noise and Lock Sound noise.
These two are really unnecessary for the most part.
How-to: "Settings" -> "Sounds" -> "Lock Sounds" turn "OFF" and "Keyboard Clicks" turn OFF -
Turn of that Equalizer: yes, according
to Apple, turning of Equalizer will save little battery time!
How-to: "Settings" -> "iPod" -> "EQ" -> "Off" -
Turn of Sound Check: iPhone provides
Sound Check feature to adjust music volume to keep consistent range for all
songs. Most of the time it does not work (at least for my
songs). So you can turn it off to save some juice.
How-to: "Settings" -> "iPod -> "Sound Check" turn "OFF" -
Audio encoding: compress size of your
music file for better cache purpose and encode using MP3 or AAC encoding.
AIFF and some other formats are not good and eats up CPU cycles
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Room Temperature: Keep iPhone in room
temperature and do not charge your iPhone while it is in carrying case or
cover. This keeps battery in ideal temperature even when charging.