Who is for people. Which is for things, places, and ideas. The student who finished. The test which we reviewed is the usual miss unless you mean a non-person. Relative pronouns as a set are in relative pronouns.
Person or not
A named person, a teacher, a teammate: who (or whom if it is an object). A school, a score, a method, a city: which or that. The coach which stayed late is wrong. Change it to who.
People versus things with that is in that versus who. Places often take where or in which, in where versus in which. Subject versus object for people is in who versus whom.
The bottom line
If it is a person, start with who. If it is not a person, do not use who.
Start practicing
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