See the blood red skies
And the dried out seas
No one gives a damn
That's what worries me
Oh look at me, I'm posting finally. Stupid lack of going on for Gaia much.
Anyways, I became a DM by choice as we all wanted to start playing. None of us had any experience but I was arguably the best storyteller in our group and I have a knack for keeping things fair. My first experience, though, was amusing. I drew up a dungeon for the party to go to. The first door they went to was unlocked. However, they didn't check this, or rather anything. They threw the Dwarf Wizard into the door. It didn't break so the Half-Orc Cleric of Cthulhu (do NOT ask) kicks down the door. He got hit by six javelins from the orcs they alerted in the room. That started a very fun, quick session of us learning combat rules.
Running games is very fun to me. I get to make great plots, awesome turning points, and I get to change the story based on what the characters do. I usually use a party NPC when it's necessary, though, so that gives me a chance to interact with the party much more personally. But giving them a world to play in is so rewarding to me.
The best thing about being a DM is leading your players through a plot you've made, only to watch them do something you didn't plan for. I find DMing to be fun since that gives me a chance to show the players the effect they have on the world. The worst thing about DMing, though, is trying to keep it fun for everyone. Most groups have players who play for different reasons. For example, my group has a player who only plays to make jokes out of it, though he's a good sport and shuts up when I need him too. It's impossible to cater to everyone, though. Another horrible thing, though, is when you have to tell a player no.
If there's anything a brand new DM needs to keep in mind, I think the best advice is to let the players do what they want within reason. Remind them if they're breaking out of character, but let them do what they wish. The game revolves around the adventuring party. Also, no matter which edition you play, do not be afraid to put your players in a situation that might definitely kill one or two of them. Sometimes a great boss fight will get an adventurer killed. It's part of the game, they can be resurrected or they can make a new character.
EDIT: My signature is very much related to DM-ing. Just saying.
Witness the wood's demise
And the grayish air
People die like flies
Forever
}{Mercenary - Horizon}{