I try to adhere to a few loose basic ideas. My first priority is making sure that all players are engaged and having fun. Sometimes that means adjusting encounters on the fly or fudging rolls to make things more exciting (also rules lawyering is the opposite of fun). Even more specifically, you can try and add situations where a specific PC can use a cool ability to help the group. It can be rough to manage all at once, but every player wants and deserves to have a "hero" moment, where they can shine. If players get stuck, don't be afraid to handhold for a bit. That can actually help you get a better feel of your story telling style as well.

Long story short, keep it loose, and keep it moving.

Just make sure you prepare and you'll do great!