Hello, everybody! I have not had the Droid for many days but I have experimented with it and previous devices of Android (the G1 in particular) and I culminated a list of DO's and DONT's for the phone, as well as the best thing to do for your phone; a power cycle. (Don't waste my time on the "it doesn't matter if you discharge all the way down", because for many of us it does.)
Here is the link on Google Mobile Help: http://www.google.com/support/forum/p/Google+Mobile/thread?fid=574d6cee673440ab000477ca90387908&hl=e...
Or, read it here.
Discharge phone until it won't turn on (red LED is showing), then recharge until the LED is green. Leave it like that for two hours (DROID USERS: Leave it for one hour instead) (ALL USERS:Make sure the phone is on when you start the recharging process). Repeat this process about 3-6 times a month to get maximum usage. Also, to quickly kill battery turn on Wifi/GPS/3G/Brightness to 100%/Screen never times out and leave the camera application going. This will burn it out in a matter of hours. (If you constantly switch between those options, get widgets. I have one for 3G and the Power Control widget of Donut 1.6).
DOs and DON'Ts
DON'T let apps run. Those are slurping your battery like soda, so get TasKiller from the market. (Exception for Droid)
DO keep the display as low as you can have it depending on the light situation. (Use automatic brightness if you can)
DON'T use the phone if it is hot! Let it cool before use to save battery (batteries last longer when cool than when hot).
DO use the camera sparingly! Take a picture, go home, TasKill the app quickly. My tests have shown the camera can deplete battery life by 20% every hour (Exception for Droid)
DON'T use the phone right after a healthy, full charge or after turning it on. Right then it's getting syncing, apps, network, 3G, wifi, GPS, etc together, so leave it alone for about two minutes (five is best) before use.
DO:
delete texts
refresh browser
clear market cache
clear youtube cache
clear IM/sign out
clear any other cache (found in the Manage Applications in settings)
Keep widgets on screen such as the 1.6 Donut widget Power Control that help you control settings
So like I said, with this you'll experience around an extra 10-12 hours of battery with these tips. It's been 6 and a half hours (since 8 AM to 2:30 PM) since the phone has been off the charger, and I'm still at 87% with some heavy browsing, Android Market, downloading/uninstalling, and texting. I hope these tips help you! 
NOW, with that said, there are exceptions to this for the Droid and any 2.0+ devices:
DON'T download a task manager. Android 2.0 now efficiently handles applications in the background. TasKiller and apps of the like are not needed anymore (ANDROID 2.0 ONLY, PLEASE. 1.6 AND BELOW STILL MUST USE TASK MANAGERS.)
DO use automatic brightness if your device has it. This saves battery life because the brightness of the screen changes (amazingly accurate) to the amount of light in the room. If it's dark, it dims the screen. If it's bright, it brightens the screen.
I have gone from 6 hours of heavy usage to about 10 hours on the Droid because of these tips. I hope they benefit you !
!
