When I write on spec, I write for myself. If a producer wants me to write something, then he is going to pay me. I don't know if it can be learned. Just just have to keep writing and writing, learing what sounds natural and what doesn't. If you mean the end of the first act should come around page 17, then I don't agree with Lew Hunter.
Writing is art and art has no set fast rules.
Good is good and bad is bad. I have writen scripts where the plot point at the end of the first act doesn't come in until page 30 or 35. It drives me nuts when I see people telling others than a certain thing has to happen by a certain page. So many young writers ruin good work because the tailor their work to fit someone else's ideas. Thanks, Jan Bergmans, Belgium.