Writing a screenplay is hard. Writing good dialog is damn near impossible.
Damn near-not completely. A lot goes into crafting decent dialog that sounds fluid, natural, and isn’t heavy-handed. Jack Nugent of Now You See It and Lewis Bond of Channel Criswell both tackle this topic in their own video essays, which offer excellent insight into what the purpose of dialog is, when to use it, and how to use it effectively.
There is a lot of advice out there for screenwriters looking to make their dialog better, but what I like about these videos, specifically Nugent’s, is that they don’t treat dialog as an impediment to the image. Many times we hear “show it, don’t tell it,” or “don’t say with dialog what you can show with images,” which, for the most part, is true, but those axioms tend to paint dialog in a negative light-as if it were a lesser art form than cinematography or editing. But dialog, when written well, can add dimension, beauty, and dynamics to a scene that would be impossible with silent mediums.