The title change from "Season of the Witch" to "Mean Streets" was inspired by a quote from Raymond Chandler: "Down these mean streets a man must go." Film critic Jay Cocks suggested the change to Martin Scorsese, who thought it pretentious at first, but eventually came to agree that it was effective.
To really get inside Harvey Keitel's drunken scene, the camera was actually strapped to the actor while he swayed about, and under-cranked to give it a woozy, drunken feel.
The innovative use of the hand-held camera was largely down to the fact that the film's meager budget didn't stretch to laying down lots of tracks for all the tracking shots.
The voice-over narration in the opening of the movie ("You don't make up for your sins in Church; you do it on the street; the rest is bullshit and you know it.") is actually not said by Harvey Keitel (the character we are intended to believe is thinking these thoughts), but Martin Scorsese. Scorsese felt that using a separate voice to make the distinction between Keitel's thoughts and actions was necessary. Scorsese borrowed this technique from Federico Fellini, who used it in I Vitelloni (1953).
Martin Scorsese: He appears a further two times, in addition to his credited appearance as Jimmy Shorts. First, he is visible in a "portrait" with Harvey Keitel (for one frame) in the opening home movies and main title sequence. Second, his voice appears as narration: "Father, I'm not worthy of your flesh."