If you have a newer phone ICS - jellybean I seriously would not put that on your phone. Android manages task by itself. In many ways adding a task killer will do more harm. Also even if you kill a task a lot of time Android will start it back up after mere seconds. Let the phone do is job... That's how it's programed.
Lastly when you get rid of task or "swipe away apps" a lot of times you are only killing the interface state. The app is still running in the back ground.