The 10 Principles of Good Design by Dieter Rams are timeless. This video with Rams does a really great job of going over them.
Guidelines for constructive and empowering design feedback and critique
I put together this list of core guidelines for critique and feedback that will help you run and participate in better feedback and critique sessions.
How to determine if something is well designed: The Design Critique Rubric
How do you determine if a feature or product is well designed? You don’t just guess. It’s not a question of personal opinion. Use this rubric to know.
Guidelines for thoughtful product design
You can use the below guidelines to check if your product is ready to ship (or if your prototype is being thoughtful enough), and you can use it as a core way to critique other products.