I’m really struggling with writing dialogue that sounds like real people talking. Can you throw a struggling writer a tip?
Try something that helps John Green’s dialogue and first person narration feel casual and thus “real”: He replaces the articles a, an, and the with the demonstrative adjectives this and these. From The Fault in Our Stars: “There was this tunnel that these two kids kept crawling through over and over…” When I sub in the usual articles, the sentence gets stiffer and thus feels less like a real person talking: “There was a tunnel that two kids kept crawling through over and over…” I prefer the subtlety of this technique to writing you know or like into dialogue. Give that a whirl and see how it works for you. Mix it in with other techniques, of course, as variety helps give writing a natural flow.