Past actions and events use would or used to.
I would/used to surf all summer when I lived in California.
But used to refers to past states.
I used to love you. Not, I would love you.
Used to also refers to past regular habits.
I used to eat junk food. Not, I would eat junk food.
In seeking clarification of these explanations I consulted Michael Swan's Practical English Usage. P.634
I am not a teacher.