Same here. I was camping with a friend in his back yard when I was maybe 13 years old, and he told me about "First Blood". It was a good read, and I was excited years later to get word that a movie was being made. (My friend, "Scrap Iron", went on to become a top brass US Marine working in the Pentagon.)
I also remember one day, while working in the family cotton fields, my cousin told me there was a movie coming out in which apes ruled the world, and humans were slaves.
Days long past, but well remembered.
Around 1976 or early 77 I read a paperback book called “Cross of Iron”, it was fantastic and I thought they have to make a movie of it but then I looked at the 1950s date of publication and realized there would be no movie, well it turns out they did have the movie coming out within months of my reading it, that was such a great stroke of luck for me and a great movie it was.