Test S as a multiplier
An S can pluralize nouns and form third-person verbs, making it one of the most flexible tiles. RATE becomes RATES; PLAY becomes PLAYS. But not every noun takes a regular plural, and mass nouns may rarely appear in plural form.
Know the -ES triggers
Words ending in s, x, z, ch, and sh commonly add -es: BUS/BUSES, BOX/BOXES, WATCH/WATCHES. Consonant + y changes to -ies, as in CITY/CITIES, while vowel + y simply adds s, as in KEY/KEYS.
Build regular past forms
Most verbs add -ed, but silent-e verbs add only d: LOVE/LOVED. Consonant-vowel-consonant patterns may double the final letter, as in STOP/STOPPED. The letter rack must contain the transformed spelling, not merely the base plus E and D.
Treat grammar as verification
A letter sequence can look plausible without being an accepted form. After generating a plural or past tense, say the base and rule aloud. If the meaning or grammar is doubtful, verify it instead of assuming every theoretical suffix combination is a word.
Quick review
The strongest habit is to separate hard constraints—letter counts, length, fixed positions—from helpful clues such as frequency and familiar patterns. Use the tool to narrow possibilities, then use meaning and context to choose.