Answer:
Past habitual actions are written in the imparfait. (if it is a recurring habit that doesn't just occur one time and end, I would say use the imparfait)
Statements that translate as "used to" in English are written in the imparfait tense in French (par exemple, quand j'étais enfant(e), je dansais beaucoup.)
Because mental states don't usually have a clear, defined beginning or end, we use the imparfait with them. (c'est vrai; ongoing events always use the imparfait)
When saying what time it was at a certain point in the past, you must use the passé composé. (it is a completed action, so you would use the p.c.)
When saying a person's age in the past, you must use the passé composé. (see above)
Explanation:
I took French class for four years in high school and learned a lot about the p.c. vs. the imparfait. :)
I am not so sure about the last two though so if they are incorrect, je suis desolée!
