A few random DMing tips I've been mulling over:
- Use Voices: Using unique voices almost never hurts. Make up a goblin voice, a kobold voice, and orc voice, etc. They'll be silly and inconsistent at first, but eventually they'll be at least consistent, and you won't have to tell your players the voices sound like those of orcs.
- Use Lingo: Not all the time, and don't use it ambiguously. But if you've got an encounter with orcs, make up one orcish synonym for "weakling" and have them shout it in reference to the PCs. Or have a gnome merchant call longswords something other than longswords. Like I said, not too often, just a light sprinkling.
- Customize Magic Items: Does that amulet of natural armor cause the wearer to grow tufts of fur or scales? It matters. The little things are where the game comes alive or falls flat.
- Gloss Over Boring Stuff: Have a huge long political intrigue encounter prepared but the players are bored with it? Suck it up and move on. Convey the necessary information and get them to something they find interesting.
- Dwell on Interesting Stuff: The players having way too much fun talking to some random-ass nameless NPC about the booming rainbow trout industry? Whatever, go with it, they're having fun, and more likely than not you can make that random NPC important later. Just don't forget the details you made up on the spot.