Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.
There are 5 common mistakes junior designers make. They focus on the look instead of usability, commit type crimes, work outside of design systems, lack confidence when presenting their designs, and ask for feedback too often.
Visualizing user attitudes and behaviors in an empathy map helps UX teams align on a deep understanding of end users. The mapping process also reveals any holes in existing user data.