How do I add fog, smoke, and maybe fire to my scene?

How do I add fog, smoke, and maybe fire to my scene?

Since you are posting in Compositing… i guess using any footage of fog, smoke, fire with a black or green backgound… maybe even already made ready to use with transparent back ground ?? FX-people to make shots with black background for this… since the invention of FX in the early days of photography…