Why the Q is a trap
Only one Q exists in the bag, it's worth 10 points, and nearly every English word that uses it demands a U as well — a second specific tile you may never draw. Hold a Q too long and it clogs your rack for turns; get caught with it when someone goes out and it costs you 10 points at the finish (20 in effect, since your opponent gains what you lose in many scoring variants). The entire problem dissolves once you know the handful of words that play the Q with no U at all.
The essential four
QI (plural QIS) — the circulating life force in Chinese philosophy. The single most-played Q word in modern Scrabble; on a double-letter square the Q alone is 20. QAT (plural QATS) — a shrub whose leaves are chewed as a stimulant; also spelled KAT and KHAT, both valid. QAID (plural QAIDS) — a North African chieftain or local governor. QOPH (plural QOPHS) — the nineteenth letter of the Hebrew alphabet. Learn these four and the Q stops being scary; everything below is bonus.
The extended list
QANAT — an underground irrigation channel of the ancient Middle East. QINDAR / QINTAR (and QINDARKA) — Albanian currency subunits, a gift when your rack is drowning in vowels and an N. FAQIR — variant of fakir, a religious ascetic. SHEQEL (plural SHEQALIM) — Israeli currency. TRANQ — slang for tranquilizer, and rare in ending with Q. NIQAB — a face veil. QWERTY — the keyboard layout, valid in many modern lists. Availability of a few of these varies between dictionaries — this site checks against ENABLE; your app or club list may differ on the newest additions, so test before you commit in a tight game.
Q strategy beyond the word list
Knowing the words is half the job; the other half is knowing when not to use them. If the board offers no premium square for QI and your rack is otherwise healthy, dumping the Q for 11 points flat may waste its potential — but holding it more than two or three turns hoping for the perfect spot is almost always worse. And don't forget the exchange: trading the Q back to the bag costs a turn but un-jams your rack, which is often worth more than a forced 12-point play. The math is simple — if holding the Q is costing you 10+ points a turn in flexibility, let it go.
Defensively, once the Q is on the board or in your rack, count it: there's only one. If you've seen it played, every U in your rack drops in value; if it's late game and the Q hasn't appeared, avoid leaving yourself one tile from going out while it can still land on you.
Words With Friends notes
The core list works in WWF too, and the Q is likewise 10 points there. WWF's dictionary is slightly more permissive and its board puts bonus squares in different spots, so QI parked on a triple-letter square (30 for the Q) comes up even more often. The free test-play in WWF means you can always verify a fringe word like QWERTY costs nothing to try.
Check any Q rack in the Scrabble finder or WWF finder. More guides: every two-letter word · Wordle strategy · history of anagrams.