Como estuvo la fiesta? is asking you for your reaction, a sort of "What did you think of the party? How did the party turn out?" kind of question. This is a combination of the use of the preterite (it's over and done with, from your point of view) and using estar for personal reactions. English has no single verb equivalent for that use of estar. Just learn some of the phrases as you encounter them: Estas muy guapo/guapa = you look really handsome/pretty; ?Como esta la sopa? Esta muy rica. How's the soup? It's really tasty. And now you know Como estuvo la fiesta? Estuvo fenomenal! (Sorry about the missing question marks and accents, guys.) Jannn

You have to use PAST TENSE because It happened in the past ¿ Còmo estuvo la fiesta ? But you can use SIMPLE PRESENT to ask about a past party ¿ Què tal la fiesta ?

¿Cómo estuvo la fiesta?, ¿Qué tal estuvo la fiesta?

as you may have noticed, by the answer of esteban, the two sentences may show to different meanings. the problem is that "fue" is the past of "to be" and also the past of "to go". so, if you ask: como fue la fiesta? people will understand you are asking on how the fiesta developed, well, bad, boring, etc. on the other side, if you ask "como era la fiesta? it will be understood that you are asking about the qualities of the fiesta, that's to say if it was a formal, informal party, for youngster or oldies, improvised, well organized, etc. so, esteban answer will be synonimous of "como fue la fiesta?. de second is synonious of Que tipo de fiesta era? What kind of party it was?. sure it is a bit confusing now. these two frases are quite colloquial.

"como estuvo la fiesta?" this is the more natural for me...