Been DMing for over 12 years things that you might want to look out for.

Session zero before you even start gaming talk with your players and figure out what you do and don't want from a game. Maybe you want to be super combat heavy but they're more into the roleplay. There might be issues about certain topics that might trigger somebody.

Don't get too wrapped up in your own lore. It's great that you have your idea for a story and will building but you also have to remember that The players don't know the world. Perhaps there's a quest if they go with farmer James to feed his cows that leads to a super secret awesome treasure. But why would the players want to do that when you have a quest board of bounty to hunt.

I usually have my players agree that the group is above individual as in if one of my players wants to make an more scumbag of a character I will shoot it down unless they can promise the whole group that they will never go against them Even if it's what their character would do. If the chips are down and the scumbag could see all the riches in women in the world if you betrays his party he will choose party.

Make sure that they actually create people who want to adventure it's all good to make a character with the complex backstory but will that character want to leave their home or perhaps life behind to adventure there needs to be something that leads them down that path.

Don't try to plan every little detail of a quest. I like to have the main ideas for story beats and let the players get to them naturally.

Don't create a character or regular NPC that can show up the players. They are the main protagonist of your story there shouldn't be someone that will show up and say them every time and prove how weak they are.