There have been two well-publicized (well, within the Scrabble community) of cheating in the last ten years. The first was a person that wore a billed cap to disguise his eyes so he could look into the tile bag when he selected tiles. The second was a younger player that had been seen hiding tiles about his person before some of the games. (Tournament rules require the tiles to be “squared” on the board after each game to demonstrate that all 100 tiles are present. Picking up the tiles at the beginning of the next game is an opportunity to divert certain tiles, such as blanks, S’s the X or Z, etc.)
Word lists are forbidden during tournament play. Some clubs will grant newcomers the use of a cheat sheet (all of the 2’s and 3’s, short words containing J, Q, X, or Z, plus vowel-heavy words), at least until some level of accomplishment has been reached.
While the top players pretty much know ALL of the words up to 8 letters, they are still able to beat the best robots, who absolutely know ALL of the words up to 15 letters! How can a human, with a fallible memory, compete with a machine that never forgets a single word and will always find the best play based on score for the play, how it affects the board, how it affects the rack leave? (This is the model that one of the first computerized player used.) The top players analyze the opponent’s last play – the letters used, the placement, etc. – to try to determine what the opponent had left on their rack. Board vision is much harder to teach to a machine than to a human being. For now.
The latest wave of robot players use a simulation mode to help model the best play in any given situation: the computer decides on about ten possible plays (based on older algorithms - see above), then, for each candidate play, it will assign various possible random racks for the opponent, and determine the best possible response the opponent could make based on that potential rack, then select the play that has the most advantage over the possible plays the opponent could make. This is a one-ply simulation, and while it may not be possible to run through all possible racks the opponent could have, running through, say, 10,000 simulations for each possible response has a fair amount of accuracy. If the computer has selected 10 possible plays and runs 10,000 simulations for each play, that is only 100,000 simulations for each play. Depending on the speed of the computer, this can usually be done in just a few seconds.
Of course, those programs can usually run simulations with more depth. However, if you study the single-depth simulation, you can see that the likelihood of one of the random racks generated for the opponent is very small, so the selection of possible opponent racks for a second round of simulations is even LESS likely to produce reliable results, and the cost of squaring the time required to perform the simulations (if 10,000 simulations take 30 seconds, 10,000,000 sims could take 900 seconds, or 15 minutes; there is some paring going on, I think).
So, what does the average player need to do well in Scrabble? Word knowledge. Two-letter words are a MUST – there are only 101 of them, and you already know most of them (although, you may not thought that UH was actually a word). You need to know vowel dumps – EAU, AERO, NAOI, UNAI – for those times when you can’t seem to draw anything but. You need to know hooks – if AN is on the board, you need to know that you can place B, C, D, F, G, M, N, P, R, S, T, V, or W at the front or A, D, E, I, T, or Y at the end. You need to know the short words (3 - 5 letters) that contain J, X, Q, or Z. You need to know high-probability bingos and their anagrams (there are 9 seven-letter words in AEINRST – haw many can you find?). You need to know words with multiple I’s (KIWI, WIKI, INSIPID, INITIAL, etc), and you need to know words with hard combinations like UW, BP, CG.
You need to keep your rack balanced: The ratio of vowels to consonants in a full bag is 42:56, or 3:4. If you examine the seven-letter words for vowel frequency, words with 3 vowels comprise the largest group, follwed by 2 vowels, 4 vowels, 1 vowel, 5 vowels, and 0 vowels. The best balance of vowels and consonants is 3:4. If you have more than 3 vowels, you need to find plays that use more vowels that consonants; less than 3, you should play more consonants.
Anoher rack issue is duplicates. While having a doubled E is less trouble than WW, racks without dupes are always preferred. Which means that if you have a doubled letter, it is almost always in your best interest to play one off.
Since bingos are such a successful scoring option, it also behooves you to try to preserve the letters that appear in so many of them. Very early on in my Scrabble career, I came up with this slogan: A Good player retains RETAINS, meaning the letters in RETAINS. Over the years, I have also added C and O to letters to keep, since they also show up in many bingos. Keeping as many of these letters on your rack will also help you move the more troublesome tiles in between bingos. (The top players average just a little over 2 bingos per game. I have had a game with 6 bingos, and recently, one of the top players set a tournament scoring record (over 800!) with 8!)
Board vision is the ability to see what the board will look after your next play, as well as having an eye out for hot spots. One poster above mentioned not leaving a Triple Word Score available, but that rule is not always the best. I have seen opponents fall all over themselves to use up their best tiles to “use up” a TWS for 21 points after I used the DLS between two TWS’s to double the points for an F and double the word on the DWS four squares away for 32 points. Yes, playing anything between two TWS’s can backfire spectacularly when your opponent plays a Triple-Triple (anything stretching betwee two TWS’s has to be 8 letters or longer, so it cannot be made without an additional letter), but if both blanks are already on the board, that decreases the chance of a nine-timer. Playing a high-point letter between the TWS’s also decreases the chances of a Triple-Triple. Decrease, yes, completely prevent, no.
Knowing your opponent can also help. If you know that your opponent NEVER plays phoneys, you know not to challenge every word that you do not know. If you know that your opponent likes a closed board, making it hard to bingo, open up the board. If your opponent has excellent bingo word knowledge and likes an open board because it allows them to get more bingos, close the board down.
tl;dr:
Expert Scrabble players have a combination of skills, one of which is word knowledge. One poster above said that strategic skills are more important that vocabulary. That’s true, up to a point. If your word knowledge is weak, then you won’t be able to consistently find the best play, since you wouldn’t recognize the word. Every other skill required to play at the top level all come back to word knowledge – the more you know, the better you can apply the other factors.