Unless your school makes it hard to switch majors, I don't think picking a major right away is super important. Going in undeclared is completely fine too! However, having a shortlist of majors is good and knowing what your interests are. The earlier you declare and stick with a major, the easier you will find picking your courses is. You should pick a major that you are very passionate about, but also one that is practical. By practical, I don't mean the one that will necessarily make you the most money right out of college, but one that you can use in a professional setting and can get a job with. You should speak with your major adviser or career adviser before making your decision as they will have information about career opportunities with each major.
Great question! I also suggest going to a career advisor or career counselor to explore what's important to you. Additionally, I agree that if your school makes it very difficult to change majors mid-way, selecting a major now might be a better option compared to being undeclared. On the other hand, if your school makes changing majors very easy, I would have DEFINITELY chosen to be undeclared because it allows you to really do some self-reflection and self-exploration before you decide on a major.
If you want to learn more about certain majors, look up your college's degree plan for that major and see what classes you'll be taking. You can also look up old syllabi for these classes or flip through textbooks for these classes to see if the topics interest you or ask people in the field and hold an informational interview with them to see what a typical "day in the life" of someone in that career looks like.
You may also want to do some research online. For example, a good website to see what future careers entail is ONET: https://www.onetonline.org/
This is a great question as I struggled with this when I began college. I was unsure of what major to decide when I began college, so I decided go in as undecided. I took advantage of all resources that were offered on my college campus that aided in students finding their career path. Also, prior to entering college, I took multiple aptitude tests to gauge my interests. I was able to take general classes needed for a bachelor's degree while I finalized my decision. Wishing you the best of luck in this journey!