You and fellow players are dealt two cards each whilst the dealer is dealt one face up. If your first 2 cards add up to 21 (an Ace and a card valued 10), that's Blackjack! If they have any other total, decide whether you wish to 'draw' or 'stay'. You can continue to draw cards until you are happy with your hand.
The first player starts by counting to a number up to 3 (e.g "one, two"). The second player carries on counting, adding up to, or including three consecutive numbers at a time (e.g "three, four, five"). This continues until someone reaches the number 21. At this point they lose.