If you're already pretty comfortable with the differences between ESTAR & SER, then this is for you. It's incredibly useful to have a one-stop reference for all the different flavors of ESTAR. I always wanted one when I was learning everything but never found anything!
ESTAR in all it's glory
*Ordered by importance (use). Complete ESTAR conjugation.
Present Tense of ESTAR
CONVERSATIONAL: estou » tô | está » tá
Preterit Imperfect of ESTAR
» eu estava (conversational = tava)
» você estava (conversational = tava)
This form is used so much when talking about almost anything that "was" in the past that most people assume it's with the "simple past" (preterit tense). But it's really the imperfect version - the one that describes an action that was unfinished in the frame of the story. And that is just fine because ESTAR almost always gets used that way. For example:
*You'll almost never use the simple past form of ESTAR » eu estive, você esteve.
ESTAR in the Future Subjunctive
» eu estiver
» você estiver
Usually triggered by quando & se:
ESTAR in the Present Subjunctive
» eu esteja
» você esteja
Triggered by the usual things for this tense: espero que, quero que, importante que.
the Imperfect Subjunctive of ESTAR
» eu estivesse
» você estivesse
Always think of this tense as were to be:
Rarely used forms of ESTAR
Adding these to be complete. If you're using any of these you are getting into advanced territory with Portuguese!
The Conditional ESTAR
» eu estaria
» você estaria
ESTAR in the Preterit
» eu estive
» você esteve
You only need to remember to use this verb form when talking about a place that you (or someone else) has been.
The Future ESTAR
» eu estarei
» você estará
Use the future tense to give a certain seriousness or certainty to the phrase, like this:
The Past Participle of ESTAR
The past participle translates to been, like this:
The Gerund of ESTAR
Pull this one out when you really want to impress or confuse someone. It's rarely used verbally, but you might see it in a newspaper or a legal text.