how do I close down apps without deleting them?

If you want to completely exit the apps, then press the home button twice to access the multitasking bar. Then press and hold on one of the apps, they should start wiggling, and a red minus sign should appear in the corner of every app. Press the red minus sign and the app should disappear signifying that it has successfully been quit.

http://whenwillapple.com/blog/2010/04/19/iphone-os-4-multitasking-explained-agai n/

No problem, glad I could help.

That worked prior to IOS 7. How do you do that now?

After double clicking the home button, swipe the App thumbnail up and off the screen to close it.