Do your homework...marketing is as much a shot film as the film itself....it's called momentum, anticipation, viral videos and or viral rumors, all in hopes of drumming up excitement and ultimately sales for a coming picture, filmed or not....again...film school 101. Marketing schemes are designed and begun well in advance of whatever they happen to be representin.
Marketing for ALIEN3 began before production started, when the film was still in developmental hell. I'm sure most of us know about the 'It's on Earth' teaser that was created and released before a frame was shot, and again, as we all know, the film took place in a penal colony. This has been the case for many, many films, including the yet to be released Super 8, which a teaser was released for, before production even begun.