Conjugating verbs in the third person involves following a few rules: 1. For verbs ending in SS, X, CH, SH, or O, add ES to the end in the third person (fixes, watches, crashes). 2. For verbs ending in a consonant and Y, remove the Y and add IES (carries, hurries, studies). 3. In negative sentences, the main verb stays in its base form without changing for the third person (doesn't speak, doesn't sleep, doesn't study).