When do I use imperfect versus preterite for estar? I heard there are special rules here.
Cuando estuve en Nueva York yo vi la Estatua de la Libertad
Cuando estaba en Nueva York yo tomaba el metro
I am just doing what feels right but I could just as easily be making grammar up.
Use pretérito imperfecto for actions that used to happen, and pretérito perfecto simple for actions that happened in special conditions. So
Cuando estaba en Nueva York tomaba el metro.
means
When I was [living] in New York, I took the subway.
In a present tense, you would say
Yo cojo/tomo el metro [cada día, dos veces a la semana...]
I take the subway [every day, twice a week...]
Use cojo in Spain, but be careful with its use in Hispanic America, since in many countries coger has sexual connotations.
On the other hand, this
Cuando estuve en Nueva York, vi la Estatua de la Libertad.
means
When I went/got to New York, I saw the Statue of Liberty.
Another example, this time with rain. In a place where rains a lot
Me aburría cuando llovía.
I got bored when it rained.
In the south of Spain
Me aburrí cuando llovió el jueves.
I got bored when it rained last Thursday.
Cuando estuve en Nueva York, vi la Estatua de la Libertad. is When I went/got to New York. I understand got, but wouldn't went be better said as Cuando fui en Nueva York?
This is an informal comment, a set of examples to visualize the way that a native Spanish speaker thinks about the verb estar. The rules may appear in common bibliography.
Estar is so different for us from Ser. Ser is the character of the things. Estar is the state of the things. In English, these two concepts are blended in the to/be verb.
Estuve is used when you were in a place that references a single point in time or you are declaring a punctual action of being in a place in the past. Estaba is used when you want to talk about a context that is continuous in time, a determinant of the situation that you are talking about, determining 'where you were", or what you were doing. Examples:
Yo estaba solo ayer en el examen: I was alone yesterday during the test.
Yo estuve sólo en el examen: I was the only one in the test.
Yo estuve con tu amiga: I was with the girl that is your friend. In some informal context this may mean that he kissed or had relations with your friend.
Yo estuve en casa todo el día: I was at home all the day. In this sentence the speaker is stating the fact of being at home, regardless of the time interval, emphasizing the fact and not the circumstance (la circunstancia). If you said Yo estaba en casa, that would be translated as, "I was staying at home." The emphasis is now on the circumstance, and this sentence may be used as an excuse in an interrogation to justify that you were not in a place outside home during a specific interval of time. But "Yo estuve en casa" may be used for the same purpose, but excusing yourself for a specific time and not an interval.
Suppose that you were crying all day and go to a friend, you say hi and then say: I was crying all day. It is a correct way to start a Conversation, but in Spanish...You can say: Estuve llorando todo el día. And end your sentence - that works.
But if you say: Estaba llorando todo el día, it would be improper speech. This is because when you use the second way the listener will be waiting for you to complete the sentence because you are making more emphasis to the circumstance of having been in tears, than the fact of crying. Then you must close the idea and say why you mentioned that you were crying all day.
Preterite tense indicates a more precise point in time that is now clearly in the past. Past imperfect tense is used to "set the stage," or establish a setting, or to describe something that happened over a longer period of time in the past.
I don't know that there are special rules just for estar regarding when/how to use preterite vs. imperfect tense.
Use the preterit tense to terminate the event; this event being... being.
You might ask yourself, "How can I terminate my being?", but asking questions like that might send you to the insane asylum after awhile. In English we don't think about how to terminate our being, because we have an equally, if not more, confusing verb to use.
A verb with 8 different meanings that get even more complex.
When did you get here?
I got here yesterday.
To use it in the context of your example
When I got to New York I took the subway.
Hopefully by reading these examples you can understand when to use estar in the preterit form.
Estuve mojado cuando llovía ayer
I got wet when it rained yesterday.
A more proper translation, yet not common in use whatsoever.
I was moistened when it rained yesterday.
But that sentence is an absolute translation, because was is the past tense of to be
