I just learned of a neat trick I wasn't aware of from the folks at SmartestApple.com. To selectively close apps all you need to do is this:
- Press the round "Home" button twice.
- The screen will change, showing you the loaded apps
- Press & hold any of these icons until a red icon appears on each
- Press the icon on every app that you want closed
That's it! I have yet to try this fully but will periodically give it a go to see if things improve.