Honorifics: 시, 님, and words that change entirely
Raising the *other* person, not yourself
Insert 시 into the verb to honour the subject.
가다 → 가세요. 읽다 → 읽으세요. This raises the person doing the action, so you never use it about yourself: 제가 가세요 is wrong.
Some words swap out completely.
먹다 → 드시다, 자다 → 주무시다, 있다 → 계시다, 말하다 → 말씀하시다, 죽다 → 돌아가시다. These are the ones worth memorising as vocabulary, not as a rule.
님 attaches to titles, not to bare names.
선생님, 사장님, 부장님. Attaching 님 to a family name alone (김님) sounds like an internet handle, not speech.