Make the next step clear.
Use familiar words and a visible hierarchy. A person should understand what they can do, what will happen, and how to go back.
Design for real conditions.
Try the interface on a small screen, with a keyboard, and with longer text. Consider slow connections and incomplete information from the beginning.
Treat errors as part of the experience.
Explain what went wrong in plain language and give a useful next step. Preserve work wherever possible so a small mistake does not become a full restart.