What Mr. Wilder means”…the third act must build, build, build…”,
is to make the tension of what your main character is
doing to achieve her/his goal go up, up, up, like using
a corkscrew to open a bottle of wine. The more you
twist, the tighter the tension in the cork becomes, until something
gives, the cork breaks, or whoever is screwing in the
corkscrew, decides it is time to pull out the cork with
the corkscrew.

In other words, make it more and more difficult for
your main character to achieve her/his goal until
she/he comes to a point where he/she must either
give up her/his goal, or, he/she “goes over the top”,
experiences an epiphany, and accomplishes the
goal. Each obstacle (difficulty) must be more
challenging than the last. It’s like putting your
main character on a tree branch. Her/his
opposition throws rocks at her/him until the
branch breaks. Then, he/she falls in a raging
river. Then, in the river, he/she fights to keep
from drowning until he/she comes to a roaring
waterfall. The question is, will she/he, survive
the waterfall, or not?

When you have your main character at the “waterfall”
of your story, then you have your main character
decide at that point, what she/he has to do to
survive tumbling over the waterfall. To conquer
this, the main character must overcome her/his
greatest fear of accomplishing his/her goal
throughout the story. If he/she does, then he/she
experiences an epiphany. He/she faces her/his
fear and overcomes it. Perhaps, instead of tumbling
over the waterfall, getting battered to death by
rocks, and drowning, which has been your main
character’s primary fear that has been keeping
her/him from accomplishing his/her goal in the
story, that of the fear of drowning, your main
character swims back upstream and saves
herself/himself.

This is the last event in the third act. From
this point forward, wrap up all loose ends
from your story, send your main character
to the Olympics as a champion swimmer,
and end your screenplay.

Donald L. Vasicek
Olympus Films+, LLC
The Zen of Writing and Filmmaking
http://michaelc.nextmp.net/wordpress
dvasicek@earthlink.net