The First Word
The first word of a game of Scrabble must be played on the star in the center of the board. It can go horizontally or vertically, and any letter of the first word can be the one resting on the star. Words are never allowed to be formed diagonally.
New Words
All letters added to the board in a single turn must be placed in a single row, either horizontally or vertically, and they must spell out a word. If the new letters touch pre-existing letters on the board, then the letters they touch also must combine with the new letters to form a word, like a crossword puzzle.
A player can form new words during his turn by adding letters to a word already played on the board or by building a new word at a right angle from an already played word; he must incorporate at least one letter of that pre-existing word. In other words, all new words played must be connected to pre-existing words. New words also can be played parallel to pre-existing words, so long as all touching letters form a word. The player gets points for all words formed.
Illegal Words
There are some words that are not legal plays in Scrabble. Proper nouns - words that would need to be capitalized - are one example. Also, words that would be hyphenated or abbreviated are illegal plays. Acronyms also are not acceptable plays.