I'm not really the best DM, but I did DM the Dark Sun season of D&D Encounters, and run a current campaign, so I'll give my two cents.
I haven't read the Essentials DM book(s) so I'm not sure of the advice given, but the advice in the two Dungeon Master Guides for fourth edition are really good. I think the most important thing to remember is to "Say yes". I struggle with that sometimes myself, but always error on the side of saying yes to a player's idea. If they want to do something crazy/outside of the rules, say yes and try and make it fit (within reason).
If a player is playing a rogue and they want to run at a monster, jump off a table, bounce off the wall, land behind the monster and backstab them, well say yes. Make them make an acrobatics check, and then if successful, maybe skip the opportunity attack, or give them combat advantage for doing something cool.
Another thing to remember is that as a DM you aren't playing against the PCs. Even though you are controlling the monsters in a combat, you aren't playing against your players. Even though it's fun to beat them down, and it's fun to use all the little sneaky tricks and tactics and cool powers monsters have, your role isn't to "win" against the players.
I guess the best advice is to try and make sure everyone, including yourself, is having fun.
As for "technical" tips, I like to refer to people by their character's name for everything in the game, even when calling their initiative and hits in combat. I think it helps people be more in character (I tend to run more hack and slash type games). The initiative tracker I use seems to be popular (not my pic, but I use the samething:
http://www.flickr.com/photos/mikeshea/3452607866/in/set-72157603839139671/)
I got that idea from
http://slyflourish.com/, it's a good site with DM tips, that might be helpful as well.