Are there any mistakes beginners should try to avoid when playing Scrabble?

1. Playing Impulsively
Inexperienced Scrabble players often play too quickly. Playing the first word you see is never a good idea, regardless of its points value. Scramble the tiles instead and see what else you can come up with.
Try to find common prefixes or suffixes so that you can create longer and more powerful words. And importantly, look for hotspots on the board to see if you can take advantage of them. Despite taking longer and requiring more effort, it is possible to score higher than if you play impulsively.

2. To believe that the best play is the one that scores the most points.
Good play and high-scoring play are vastly different. It is not uncommon for a play to score many points, but it has hidden downsides — such as leaving you with only consonants or only vowels, making it harder to achieve on your next turn. Alternatively, a high-scoring play could open up a higher-scoring spot for the opponent, such as when you play a word alongside a triple-word score. Is it worth earning 35 points if it enables your opponent to score 40 easily?
When choosing multiple words to play, consider their scoring potential, your ability to score in the future, and your opponent’s. It’s just as important to defend in Scrabble to attack, but the best move isn’t always the highest-scoring. Sometimes it’s the move that gives you the best chance to win.

3. Wasting the game’s two best tiles
Scrabble’s best tiles are the S and blank. Because the S can be added to most nouns and verbs, it is functional. You can make your six-letter word a seven-letter word, giving you a 50-point bingo bonus. In addition, S allows you to attach a high-scoring word to an existing one, as in the example above.
A blank can be anything you like. The game only has four S’s and two blanks, so they should only be used for high-scoring plays since they are rare. In general, it is recommended that you don’t use your S unless it scores at least eight more points than your next highest-scoring play and that you shouldn’t use the blank unless the next highest score is 25 points or more.