Answer:
1. Mental health. When you're in a relationship, you are usually close to the partner, which leads to a glimpse into their mental health.
2. Personality. When it comes to dating, there are two aspects of a person that are likeable. The first one is physical attractiveness, while the second is attractiveness towards personality. Like how you act, your their traits, etc.
3. Physical attractiveness. As said above, the physical attractiveness while dating is important. They don't have to be a beauty guru for you to find you alluring, or sexually attractive.
4. Mindset and future goals. It's important to pave the road for a healthy relationship of any kind. If you want to know more about a person, you can usually learn their future goals in life by just dating them. For example, they might tell you their future dream job or what they are planning to do with their life.