General Closing Apps Clarification

I don't use this phone often but I don't want apps running in the background after I'm done using them (Camera/maps/internet/etc). So I find myself constantly hitting the back button to close the app when finished.
Is it normal to do this or should I leave something like the Camera running in the background by pressing the home button?

Anyone know of the cpu/battery drain when closing versus leaving running as a background app? I'm familiar with holding the home button and killing the tasks manually, but is that necessary given the battery concerns?

GS4 w/ Verizon 16GB

 

I come from the IOS so I didn't really have to worry about this. I find myself browsing the web and when I'm done I hit the back button tons of times until it closes and is done going through my history.
I think I'll start just backing out using the home button and not worry about it.
If an app like Maps is running in the background, will it continue to look for location services etc or only if I open it again?