I often follow what my favourite anime studios are producing.
Let's see... I've always loved BONES. They have produced Bebop: The Movie, RahXephon, Wolf's Rain, Fullmetal Alchemist, Kurau: Phantom Memory and Scrapped Princess. They have an eye for a good story and almost everything they touch turns to gold. So yeah, anything they produce is more than worth a look in my books. They haven't made a bad series yet.
Like-wise, I'm fast becoming a Madhouse fan. In recent times, they've produced superior series like Monster, BECK, X TV and Haijime no Ippo. They seem to choose very unconventional stories for animation but what they produce is so unique.
Some studios are very much like bands and the series they produce are like their songs.