For 2 players
If you have 3 players, one person can be the master of ceremonies & you can take turns.  Place 7 cards in a row, face-down for the first player, and 7 cards in a row for the second player. Turn the first card up for the first player.  The first player must say if they think the next card will be higher or lower than that card.  (2 is the lowest card and ace is the highest.)  The second card is then turned up. 

If the player was correct, they get to do another turn, and so on – until they guess wrong.  If a player was incorrect, the player must start from the beginning again when it is their next turn.   (Remove any of the cards that were turned up and replace them with new cards that are turned down).  Players must continue guessing higher or lower along the row – the first one to finish their row is the winner.

More rules:  If the next card turned up matches the one before it (a tie), play is frozen & the next person goes.  A player can freeze a game themselves.   If they do not want to guess higher or lower (for instance, with 7 – middle card), they can call freeze & the next player gets a turn.  When play comes back to the first player, the card that was frozen (the 7) is taken off and replaced by a new card.  The first player then gets to choose higher or lower.
Optional:  For the first round only, a player can choose to change their first card.  The card is replaced and the player must continue.  If the player does not choose this option, there is no other point in the game where the player can replace a card and keep playing his turn.