The first word crosses the star
The opening word of the game must lay a tile on the centre square at H8, and the star is not just a starting mark: it counts as a double word square for the word that lands on it, so the first play is worth twice what it looks. After that, every play has to touch what is already down — at least one of your tiles must sit next to an existing one, and every square you skip over has to actually have a tile in it.