Be Open and Honest with Your Players

It is my opinion that one of the most important things a new DM can do is have an honest dialogue with their players. Being open with your players, and having them do so in return, can help in avoiding many frustrations down the road.

As a novice at the art of being an awesome DM, you're going to make mistakes. You can't avoid them. But that's okay. Just be upfront with your players. Let them all know, even if they already do, that you're new to being a DM and that you're going to make mistakes. You're going to do things that frustrate them, make them go crazy, and things they just outright hate. But tell them that you want to be the best DM you can be and ask them to be patient with you, and more importantly, to be honest with you. If you're DMing for a group of people made up entirely (or almost entirely) of new RPG players, then you're even better off. They're going to make mistakes too so you're all in the same boat and can learn together.

The easiest way to get feedback on your DMing is to talk directly with your game group at the end of each session. Ask your players if you did anything they didn't like or if there's anything you could've done better. If they give you answers, then take their concerns and criticisms seriously, but not personally. There's no sense in getting offended. Take their advice to heart and try to do better next time.

As with most most other things, knowing your DMing weak points will allow you to address them directly. Getting direct feedback from your players lets you know how you're doing. Maybe you only have little things to improve on, maybe you're delivering an adventure that's way off track from what your players were expecting. Regardless of where on the spectrum your shortcomings lie, player feedback will allow you to correct those shortcomings and provide the most fun experience possible. And, it usually goes hand in hand that when players are having fun, so are you as the DM.