Helpful rules lawyers who say "Oh! I know how grappling works, it's X and Y and Z" are your friends.
Annoying rules lawyers who say "That's now how grappling works" should be shut down immediately and reminded that the GM is trying to keep the game running smoothly, that the current way you're handling things is now houseruled, and that any issues can come up after the session.
Stickynotes in your rulebook for places you might need to find in a hurry are useful.
When you write down stuff your players might encounter, make sure you copy all their stats down into your notes too so you don't have to cross-reference with the Monster Manual or whatever.
When you're introducing your new setting, players love props. Don't just tell them about your setting, show them. My group loved it when I gave them 'travel brochure' type stuff. Let them have reference materials, and let them have a map of common-knowledge city/region stuff that can just sit on their side of the table that they can just pass around whenever they like. Same with new races, make fact sheets and stuff that they can refer to. Not just stats, but stuff like "this is what people think of this race, this is what they look like, this is where they're from".
In terms of maps for your urban area...Well, do you have a super detailed city map? You might want some mid-level overviews, like "This is a map of the different town wards, here's some description of what they're like" so they can get a good feeling of it on a neighborhood level.
Have a page in your notes with a bunch of random names from different races, and a couple blank lines for each one. Players WILL want to know the stableboy's name. So, grab a name out of your notes (so you don't have to think it up on the fly), and scribble "stableboy" next to the name in your notes. It'll help you worry less about them dragging new NPCs into the game.
On the other hand, if the players don't find one of your main NPCs interesting, just drop them. I mean, everyone knows that players like to derail whole plots by stabbing the wrong people or just not going where you expected, but your players are also likely to find your innkeeper or town guard with the cool backstory and characterization annoying/boring. If your players don't want to interact too deep with a certain NPC and it's not vital to the plot, seriously, don't make them. It can be really frustrating and you might not even notice you're doing it, but try to pay extra attention to which NPCs the players 'like' because their favorites won't be your favorites.
And this differs from group to group, but it wound up being real important in mine. Do not expect the players to always drive the plot. Some groups are really good at investigating, but if they start to lose momentum, pick that pace back up. If they missed some hints, a guy drops dead at their feet clutching a mysterious note. If it's their fourth day at the inn and they don't seem to be going anywhere, someone kicks in the door. Don't railroad them--but keep throwing them things that they need to react to, one way or another, preferably in ways that nudge them towards finding out What's Really Going On.
Doesn't matter if you didn't have anything planned, or even if you have to pull a new antagonist's lieutenant completely out of your ass...but sometimes if you don't move the plot forward yourself, your players will end up inventing the beach party, or spending a whole session investigating exactly what the properties of that strange pocket dimension are (and if they can sharpen a sword with the disintegrating field at the edge).