He began acting in New York city. As he didn't have much money he usually slept at friends houses, or the streets; he was homeless.
After four years at HB studio, Pacino successfully auditioned for the Actors Studio. It's a membership for professional actors, theatre directors, and playwrights.
Al's first acting gig in a film was in 1971, a film called The Panic in Needle Park, which he played a heroin addict, which brought attention to himself by director Francis Ford Coppola, who later on ended up directing the film The God Father. Al Pacino played the role Michael Corleone in the movie, (he even beat out Robert De Niro for the role) which was the God Father's son. His performance got him an Academy Award nomination.
2 years later he played in many other movies such as Scarecrow, Serpico. In the sequel to The God Father, he starred again as Michael Corleone, which was the first sequel to win the Best Picture Oscar, and then nominated for his third Oscar. Later on The God Father became trilogy, which he was in again as Mike.
His most famous film the he's in, in my opinon would have to be the classic action film, Scarface which was released in 1983, about Tony Montana (Al Pacino) a small town chef who turns into the most powerful drug lord.
http://en.wikipedia.org/wiki/Al_Pacino