1. Wrong: It was clear that Elias loved games and books.
Better: Clearly, Elias loved games and books.
Explanation: It almost never has a clear antecedent. If you can writing without using it, do.
2. Wrong: In Zadie Smith's book, she creates complex characters.
Better: In her book, Zadie Smith creates complex characters.
Explanation: The pronoun she can't refer back to the adjective Zadie Smith's. Remember that all possessives are adjectives. To correct the problem, use the author's name as the subject of the main clause.
3. Wrong: This demonstrates everything Enzo's been teaching about music.
Better: This scene in which they fall in love while playing the guitar demonstrates everything Enzo's been teaching about music.
Explanation: In speech, this can be a demonstrative pronoun or a demonstrative adjective. Demonstrative pronouns work very well if the listener can see what the speaker is gesturing towards when calling something this. In writing, the writer can't gesture to whatever this is, so in writers should use this only as a demonstrative adjective (by putting a specific noun or noun phrase after it).
4. Wrong: Josefina could do anything related to art and science and math, and it shows in her great attitude in those classes.
Better: Josefina could do anything related to art and science and math, and her STEAM abilities show in her great attitude in those classes.
Explanation: As a general rule, don't use it, but to explain more specifically what's going wrong in this sentence, the it could refer to anything, art, science, or math.
5. Wrong: Maja wanted to ride with Camille, which created an awkward moment for everyone in the car.
Better: Maja wanted to ride with Camille, an unrequited desire that created an awkward moment for everyone in the car.
Explanation: In the original sentence, the which could refer to Maja's desire, Camille's hesitance, the fact that they're riding somewhere, etc; in sum, the which doesn't have a single, clear antecedent.