I've had people tell me that you can force close apps on the iPhone by double clicking the home button then holding an app in the pop up and when it has a little minus beside it tapping it, apparently that closes the app as just hitting the home button when you've finished using an app doesn't close it?? I'm confused as I thought that removing the app from the menu when you double tap the home button just removes it from the list and pressing the home button to close an app does just that... Can anyone help me find fact from fiction with what I've been hearing please?
If you're in an app and you press the home button, think of that as putting the app in the "background". When an app is in the background, it could possibly still be doing things, or just be waiting for you to switch back to it.
When you double-tap the home button and tap-and-hold on an app until they start wiggling, you can press the X to remove the app from the background — all that means is the app won't be doing anything in the background anymore, and will have to load all of its resources the next time you launch it.
Force-closing an (unrepsonsive) app is another thing entirely, it's like killing the app while it is still in the "foreground" — and to do this, hold down the power button until the "slide to power off" screen appears when you're still in the app, then hold down the home button until you're dropped back to the homescreen.
I agree with Benny, with a caveat - GPS apps that you are running in the background ARE using significant power (and other resources). If you are NOT USING TOM TOM (or some other GPS using App) for example, don't just move it to the background, make sure you close it.
Most of the time, I've not bothered caring about background apps. Developers should have enough sense not to drain your battery considerably when their apps still run in the background. The one app I DID have to kill was Skype, as it wiped out my battery overnight. This has likely been fixed, as it no longer seems to do this.
When iOS runs out of resources, it auto-kills background apps (if they are leaving anything running), but the app is still listed as one you have opened before, even after restarting the phone. Something I recommend doing is restarting your iPhone at least once a month, as well as before installing an iOS update.