Adhere strictly to the play loop: (1) The DM describes the environment. (2) The players describe what they want to do. (3) The DM narrates the results of the adventurers' actions (sometimes calling for a roll first). Repeat.
The DM is really only talking during steps 1 and 3 and essentially creating the context for the players to make decisions, then saying what happens when those decisions interact with the context. Then you set up the context again if something has changed. Otherwise, you can safely be quiet.
When setting up the context, I try to limit myself to 3 to 5 sentences, tops. Just enough to lay out the basic scope of options that present themselves. Then ask, "What do you do?" More options may present themselves after the PCs take action. Keep that play loop... uh... looping. Even in combat. Avoid saying what the characters do. Just say what effect what they did has on the situation.
But really the question to examine is what were you being verbose about exactly?
Basically, this.
My descriptions. I was careful not to make anyone's decisions for them (I hate that), but when players wanted to ask questions or take actions sometimes, I was still going all motor-mouth with my descriptions of this weirdo world I made. I suspect my own anxiety about DMing for the first time and my enthusiasm about this world I've spent so much time on got the better of me, you know? But I also know I talk too much in general, so I'm hoping to find tricks for reining that in at the table.
Congrats on taking the plunge. Anxiety is a normal reaction to the juggling act that is DMing for people live and in person.
It's a tough one because the players only know what you tell them, so you have to give them the relevant details. But, as you say, you don't want to just jabber at them.
I think iserith is spot on. Stick with the play loop, answer the players' question so they have the details they need to have the context required to make informed decisions, then shut it. As it were. Infinitely easier said than done. Learning what's necessary and what you can trim takes time.
Look at modules and their block text, call-out text, read-aloud text and find ones that you like, then try to emulate those. Also, look at books, blogs, or articles about writing fiction. Especially how to handle description. Quite often they'll suggest sticking with no more than 3 pieces of information about a given subject (person, painting, room, etc). If it's important, mention it. But the details, the color of someone's hair, eyes, clothes, jewelry, shoes, fingernails, toe jam, etc aren't necessary...unless they are. The flip side is to not
only point out the really important stuff because your players will learn that you
only mention the important things and immediately know where to go and what to examine closer. It really is a juggling act.
Lastly, it may seem counter-intuitive, but start with the mundane stuff and end with big stuff (monsters, big attention drawing things, etc). This is because if the first thing you say is "28 orcs" then the players won't be listening to a word you say after that. They'll be grabbing their dice and likely already rolling initiative before you've gotten to the part about how they're having a combo book club and knitting circle.
