I am most pleased with these two sentences:
She didn’t want to fall back on the old familiar routine she had done at many local high schools. It was juvenile, and felt worn out, with punchlines that were way too predictable.
A series of words helps show how ordinary her stand-up comedy is: fall back, old, familiar, routine, local, juvenile, worn out, predictable.
The choice of the word routine, instead of stand-up, or comedy, or jokes, keeps the theme flat and boring, whereas those other words would liven it up.
By placing predictable as the last word of the sentence, the reader also has a chance to find the sentence predictable, so that I don't have to show a single joke from the routine. A good punchline always comes at the end, to deliver the punch. Here, I took away the force of the punch, leaving a string of words leading up to predictable which should give the reader the most opportunity to correctly guess how the sentence would end.