* Use caer bien / caer mal in terms of liking or disliking a person.

(If you use GUSTAR to express liking a person, it tends to have romantic connotations, as in you «like like» them).

*Importar is used to express that something matters to you, that you care about it.

* «Caer bien / caer mal» and «importar» work like GUSTAR verbs.