Playing a poker face is the basic way to act unreadable in the game poker even though you have a good card you won't show your emotions instead act as if you will lose. Just playing mind games with your opponents will make them bait your bluff. In the end if you don't want this kind hastle play online so you don't have to worry about your facial expressions.
it will not be called poker face for no reason but this term became popular because it was the basic strat use by poker players but a poker face is neutral reaction , if you will act as is you loose your oponnent will think that your feeling the opposite so i dont recomend that .