Deal out all cards (if there are only two people, deal for three leave the extra hand) - the object of the game is to get rid of all your cards.
The person with the 3 of hearts starts (in later games it is the julio).
A player starts a round by playing a one or more of the same card. The next player must play a higher card, and the same number of them (pairs on pairs, etc), or the player can choose not to play (though they can't play for the rest of that round).
Once no-one can/wants to play - the last player gets to start a new round.
Aces are high, and 2 is a special card (higher than an ace).
After the game, the winner is named El-Presidente and the loser is Julio. With odd number of people, the person inbetween is called the Middle Man.
The Julio gives El-Presidente their best card, and El-Presidente gets to choose any card (their worst) to the Julio.
In games of more than three, you have Vice-Presidente and Vice-Julio - they swap one card, and El-Presidente & Julio swap 2.