In crossword games that offer a bonus for playing all seven tiles, six letter words will be the least common words you play. More often, you'll play a five-letter word and hook it to an already-played tile. Still, it's useful to know some good-scoring 6 letter words, particularly those that can be made plural or put into the past tense.
The three most common are NUMBER, PEOPLE, and BEFORE. These are good words to use to make get rid of hard-to-use letters, such as both Ps, a B and an F, and a U and a B.
NUMBER and PEOPLE can both be verbs, so if you have an extra E or a D in your rack, you can make an eight-letter bingo by hooking an already-played tile.
The C tiles are tempting because they are worth three points, but they are tough to use because they are nearly impossible to hook. Using 6 letter words starting with C, particularly with an already-played tile with which you can hook, is a good way to get rid of even multiple Cs. Such 6 letter words starting with C include COCCYX, CHAINS, CLOACA.
The 6 letter words starting with S are much more common because S is the most common consonant in the English language. Examples include SALMON, SHINED, and SUPPER. The real gems are the words ending with S because all nouns and verbs can either be made plural or put into the third person. You can use these word forms as eight-letter bingos.
Rack balance is crucial for success in games like Words With Friends. A six-letter word clears almost the whole rack. It would be nearly impossible to form a bingo with the letters in the word COCCYX, but if you had an E, T, or S as your seventh letter, playing COCCYX with your other letters could yield a bingo on your next play.
There are some good ways to use the C tiles with words that begin with other letters, like BUCOLIC, RACING, and TONICS. Of course, BUCOLIC would need a letter to have already been played. In fact, one of the best tactical plays is to block open vowels with any word so that your opponent would not be able to play words full of irritating letters. It would be a case of blocking a six-letter word with a three-letter word.
As with any classification of words, knowing what's what with six-letter words is a key skill to winning at Words With Friends, Scrabble, and other word games.
There are more than 20,000 six-letter words in the Official Scrabble Player's Dictionary, Volume 6.
STARED, SPREAD, and SALIENT.
ACORNS, ASSAYS, ALLIES, and AXIOMS.