How is your setting on the auto-sync? If it's on, you may turn it off. Also if you have any weather, news, youtube updating widgets that can drain battery too. I noticed significant battery gain after turning them off. You may try battery saving app like Juice Defender too.

If none of those help your battery life, I think it must be a defective battery.

 

You can also go to Settings>Applications>Running Services to see what may be running in the background and close out of it. Sometimes apps even though it appears you closed out of it, continue to run (for example: TuneIn Radio. I hit pause and then back out of the app and the icon disappears from the notification bar, but when I go to Running Services, it still is running so I just "touch to stop") Some apps, you may not want to close out of like GTalkService. I haven't tried it, but I know that if you remove the app, it messes up with the Market.

Oh...and the airplane mode thing is for fixing the 50% bug or when "Time without signal" (under Settings>About phone>Battery use>Cell standby) is 50% or over. This basically means that your phone (whether you have great reception or not) is searching for signal 50% or more of the time which kills your battery. Putting the phone into airplane mode, rebooting, and taking it off is supposed to "fix" it temporarily.

 

The only problem with this is that the Ally powers on as soon as you plug it into a charger. As long as it's plugged into a power source/charger, it will NOT stay powered off, no matter what you do.
JL

 

That's good point. Ally powers up as soon as it's plugged to charger even if it was turned off. I don't know why LG designed it this way, but I don't have much problem with this.