The Sandwich with No Toppings

Sentences are like sandwiches with no toppings . . .

(interuption) Wait! Hold on a second! An author cannot simply juxtapose any two nonrelated items to make a literary point. This is simply not acceptable! Please try again.

(resumption) Ahem. Sentences without good word choice are like sandwiches with no toppings. Using exciting and professional sounding words will give sentences the flair that they need to keep the reader wanting more.

Here are a couple examples.
Boring --> "The student did his paper and then did something else."
Interesting --> "The stressed student rigorously finished his twenty page paper, quickly progressing to a study session for his final exam."

The second sentence, while also giving more information and a clearer meaning, conveys a tone of urgency and stress that is not present in the first sentence. It is clear and interesting. And thus, the simile is complete. Pile on choice toppings into your sentences through great word choice.