Welcome to the forum! There are some great links to study that you can access from the Wayfarer sign-in page. But the number one thing to memorize is the core criteria of a great place for exercise, exploration, or being social.
You can’t always judge whether something is eligible by today’s standards by what you see in game. Criteria has changed over the last decade, and sometimes things are accepted incorrectly. Go back to that core criteria for your nominations.
A great way to become better at submitting is to review. That way you will see what helps to make it easy to accept a nomination, and what does not.
I also recommend this post: Top Mistakes Made When Nominating, and How to Avoid Them
Use the Nomination Support and Review Support categories for specific questions. We love to help!