There are some trips that go perfectly without planning and the spontaneity of it all just makes it that much better, but this was not that trip. Trust me when I say, we learned the hard way on this one. In hindsight, there were a lot of things that could've been planned better, but we still had a great trip, learned some lessons, and we will 100% be trying it again the right way in the future.

What Not to Do When Planning a Trip to Yellowstone Part 1:
Don't assume all the entrances to Yellowstone are open all of the time. They aren't. Certain entrances to Yellowstone close during the year because of weather or other reasons. Don't just check to see if your Airbnb, hotel, or VRBO is close to Yellowstone National Park; check to make sure it's close to a Yellowstone entrance and make sure that entrance is OPEN before booking it. This will save you lots of driving time and provide more time inside the park. You can check for road closures through this link.
What Not to Do When Planning a Trip to Yellowstone Part 2:
Don't assume that not going during peak summer season will be better. Sure, there is hardly anyone around, but then again... there is hardly anyone around. The towns and cities surrounding Yellowstone basically all shut down during off-seasons becoming ghost towns. Even grocery stores and convenience stores close around 4pm everyday. This makes it very difficult to find anything to do or eat after you've seen the park from the one road that is open. It's not ideal when you want to find souvenirs, experience the local attractions, or do something fun at night. Just go during the summertime when all the workers move back to town and set up shop. It will make the experience more full.
What Not to Do When Planning a Trip to Yellowstone Part 3:
Don't wait until you get there to see about booking experiences like white water rafting, horseback riding, or fly fishing. These activities book out months in advance. If you want to have a great trip to Yellowstone, it takes some planning, booking, and paying ahead, but trust me you will be thankful you did it.
What Not to Do When Planning a Trip to Yellowstone Part 4:
Don't ignore the weather. Pay close attention to expected weather conditions during your travels and be safe. Driving in ice and snow is a whole other struggle when going up, down, and around mountains with minimal traffic. It is best to be safe and precautionary about weather conditions and avoid traveling long distances by car during winter months.
What Not to Do When Planning a Trip to Yellowstone Part 5:
Don't have too many expectations. It's good to get excited about a trip and, honestly, it would be weird if you didn't get excited about a vacation. But too high expectations when you've never experienced something before and don't fully know what the experience entails is the number one cause of feeling let down. We did this. We had high hopes for the vacation we had booked out months in advance. We had heard of everyone's visits to Yellowstone and heard great things. But because we failed to do our research ahead of time, we missed out on a lot of the things we thought were going to contribute to our wonderful experience. It's good to go with the flow and see what happens, but some things require a little more preparation. (Especially a cross-the-country roadtrip.) Our mistake. But it doesn't have to be yours!
Hopefully this guide will help you make wiser choices early on in your Yellowstone Trip planning so you can avoid any of the problems we faced. Overall, we still had a great first visit to Yellowstone National Park, just because seeing this part of nature's beauty for the first time isn't something you forget! Our group made the best of it, every step of the way. But we definitely want to go back one day, because there is still so much to see.
I hope you get a chance to see it all and embrace the wild by planning a little bit better. Safe travels!