While your Mac is downloading and installing 10.9.2, why not read up on your Threes strategy? This is one of the best Threes guides I’ve read (whereby I just accidentally admitted I’ve read more than one guide to playing Threes). I’m pretty convinced that the corner strategy is the key to high scoring. What’s new to me here is the way the new tiles are dealt onto the board:
It seems that the game makes a “stack” of twelve cards containing four 1s, four 2s, and four 3s. It then gives you a card selected from that stack at random. When the stack has run out, a new stack of twelve is created and you begin again. This means that in any 12 card sequence you will always see four of each color of card.