If you want to experience more smoothness, more speed, less lag and always have enough free memory, then check out XDA Recognised Developer Juwe11's RAM optimisation script for Android devices.

The script will optimise RAM usage on your Android device, finding the best balance between free memory, multitasking, speed of launching apps and system speed.

It means that you'll have enough free memory and you can fully use multitask since the script does not kill your app automatically when you minimise it. You should notice your system and switching between apps or launching apps will be much faster.

You'll need root access and a kernel that supports init.d.

For more information including the actual script, head on over to the modification thread.