Well i full charged it and took it to school with me for the whole day. Later on at night around 9pm its almost flat, it was fully charged at about 8am and almost out of battery life by the end of the night.
Most smartphone users soon figure out to charge their phone each night. XT is '3G' only so a bit more battery hungry on standby. But yes there are tips to try to eke a bit more out of your battery. It's not atypical for a smartphone to be flat in less than a day. Heavy GPS usage will wipe you out in an hour or so. A full reboot should clear any errant battery hogging process. Good luck
Like @oxnsox said best to check some settings on your phone. I have mine set to auto brightness and power saving mode. Also may be worth installing a battery management app. But that's a pretty typical life expectancy of smart phones nowadays.
I just got my Motorola Defy last week, I would say its battery life is surprisingly good compare to other smartphones I used. It takes 18 hours for the battery bar to turn orange after being heavily used during the day.