So an Irish waterfall is when smoke is allowed to escape the mouth and is inhaled through the nose. It's 'Irish' because it goes up instead of down.

As for how to blow smoke rings, with a mouth full of smoke open your lips like you would say 'oo', but pull your tongue to the back of your mouth. Now lift your tongue up and forward sharply, think about try to say 'nnnnnga'.

If it doesn't work people might think you have problems though...