well in hearts its negative point scoring, you DONT want hearts, except if you get all the hearts and the queen of spades you have "shot the moon" and everyone gets 50 points (which are bad, member you want the least points to win)
person with the 2 of clubs leads, if you dont have a card of the suit being played you may play any card (like forcing someone to take a heart) the one with thie highest card of the suit played has to take the 4 of them.
you cant play hearts untill they are "broken" meaning that someone has run out of cards of one suit and can play a heart.