What is the full way to exit and app?
I remember on my BB if you didnt close an app it would kill your battery.
well you can get a taskiller to end all running apps, but it's not really needed. the way android works apps will run in the background and be 'stagnant' not using any memory, so it's not really a problem on the battery and if the phone needs more memory to perform a new function it will swap it out with something not being used, however, there are some apps that don't seem to want to play nice and do drain the batt. just pay attention to to what you download and your battery life. Be careful of certain widgets too, some of them can be a major drain(i.e. some of the battery life widgets, which IMO are pointless anyways).
A gun in the hand is better than a cop on the phone.
Only the Skilled Survive
A computer lets you make more mistakes faster than any invention in human history - with the possible exceptions of handguns and tequila.
Drill Sergeant Frick's Rules For Un-armed Combat.
1. Never be unarmed.
2. See Rule #1
USMC rule # 23 of gunfighting: Be polite, be professional, but have a plan to kill everyone you meet.
You can kill apps by going to Settings/Applications/Manage Applications/ select your app and close it.
A more convenient way would be to get "Advanced Task Killer" from Market.
This isn't your BB though, while killing apps isn't a bad idea to save battery, it's not always necessary. Take a look at this thread.