Only use what you need. If you aren't using something, make sure to close it properly. Hold down the menu key and it will show you what apps are open and running. You want to have the least possible amount of processes running in the background when you aren't using the device. That's what drains the battery MOST!! All I have running in the background when my phone is in standby, is BeWeather which updates every 30 minutes.
Also turn off wi fi when you aren't using it. By going into connections and un-checking the box or turning it off in the options.
I also just downloaded 7.1.0.649 and it works very well! Especially with making sure the battery lasts a long time! But overall it's just about how efficiently you use your phone. Understand how it works and you will master your device!!
I usually leave my wifi-on 24/7 because Im connected to wifi at home, work, and friends houses.
2. Turn off bluetooth when not in use. Bluetooth is a HUGE battery drainer
I only turn on my bluetooth in the car and when bridged to my Playbook
3. Set apps to refresh 3 hours or more OR set to refresh when opened
This goes for BeWeather, Twitter apps, Facebook, Blackberry News, etc...
I follow these steps and have no problem with battery power. I dont adjust my brightness or anything else. My battery lasts from 12 -15hrs a day depending on use. I keep my wifi-on all of the time and send/receive emails,texts,tweets all day long. Like someone mentioned OS 7.1 helps a lot too, but I've had great battery power right out the box using these steps.
1. Turn brightness down to 10%
2. Battery saving mode always on.
3. Location services off when not needed.
4. Wifi on when available, off when not available.
5. 3g/4g mode only when necessary, otherwise turn off.
6. Close out all unused apps. BBM always runs and I never use it, so I deleted it.
7. Get in the habit of pressing the lock button after checking the phone so it instantly turns off backlight. Saves battery over time if you check phone a lot.
8. I'm using one of Zocster's hybrid OS's and it seems to help. Before that I think I had best battery life with .523.
I can easily make it a full day on the stock battery following the above. With my Mugen 1500mah battery I can make it two days before charging.