How to kill application on Android

Common user most of time doesn't care about RAM of his android device, about processes that running on background etc.
User who know what is RAM install apps to clear it. But we are not common users and wont install apps to kill. We gonna kill them ourselves.

You must be root, have busybox and terminal emu installed.

You can use am force-stop <package name>.
or am kill <package name>.

am kill only kills "processes that are safe to kill": i.e. a process with no running services or activities.