SIMPLE PAST/USED TO/WOULD used to refer to PAST

When referring to actions that happened in the past but don’t happen anymore (past habits/states), we do so three main ways. 

We can use the Simple Past, the expression Used to and the modal Would. 

The Simple Past is used to express both past habits - actions that existed during a period of time in the past; and past states. This period can be implied or expressed with a time expression or a clause, like, for example, in:

 When I was a child, I visited my grandma every weekend. (habit) / When my brother was young, he liked eggs. (state). 

Simple Past is also used when we talk about past events: I went to the United States in 1998 / I played soccer yesterday. 

Used to refers to past habits and states which were true, used to happen in the past, but are not true nowadays: 

On Sundays, my parents used to take me to dance school / I used to hate dancing in those days / I didn't use to like dancing in those days (state verb).

These are actions that happened isolated in the past, and don´t have any link with the present, as we can observe, for example, when it comes to the Present Perfect tense. 

The most important difference between Would and Used to / Simple Past, is that the first can only be used with action verbs, as we notice in

From time to time, he would call her to ask if she wanted to meet for lunch / On weekends, I would invite my friends to play tennis.