Homebrew World Preparation

[Quickleaf]

I'll emphasize what TerraDave said. (i feel there should be an exclamation after your name, like TerraDave! is here to save the day!).

Focus on what the first adventure will be about. It sounds like you already have a slightly fleshed out skeleton of the overall campaign - good, that's all you need. Remember the story is about the PCs. When they wake up in the morning what do they hear? Birds chirping by a babbling brook? The sound of archers firing a volley? Who are the influential people in the adventure, like mentors, enemies, or contracted help? What is the PCs' motivation? Who will stand in their way? What twists and turns will your adventure take?

Answer these micro questions. Make a really good adventure. Use a healthy dose of description. Convey the feel of the world. Do this, and I guarantee your players will forgive you forgetting to name such-and-such village or minor inconsistencies.

A quick story....
I GMed for my friend and his girlfriend for two sessions. It was short, but I wanted an immersive setting that was true to traditional fantasy fiction. I had 3 days to prepare. I knew I couldn't make an entire world, so I focused on an adventure that gave off the feel of a complete world (versilimitude ) These were the steps I took:
(1) I borrowed a city map with several rivers converging in a port town, waterfalls pouring past several distrcits, a great natural stone arch over the port of entry. I then traced out a rough map of the city districts on lined paper, but I used colored pencils, which made it much more impressive!
(2) Next I determined what was around the city. A tower where wizards were trained. A mystical and forbidden forest. And so on.
(3) I thought about NPCs next. Who would be in this world? I wanted wizards to be truly powerful and mysterious. I thought of a well-dressed man who could speak with two voices at once and who wouldn't hesistate to unleash a plague on the entire city to perform his duty to the wizard tower as he saw it. I also thought of a scheming noblewoman with a soft streak in her heart who is interested in marrying her daughter to gain political leverage over the current ruler (who is opposed by a council of nobles). So, I had two powerful NPCs. While the mage would start off as an "enemy" and the noblewoman an "ally" these individuals are definitely playing the PCs for their own purposes.
(4) I knew both their characters - an apprentice mage and a healer. So I decided the adventure would focus on magic & healing. The mage was wounded fleeing his school after being framed and would be found floating in the river near death. The noblewoman, hoping to profit from the mage' misfortune, contracts the healer to care for him. The well-dressed archmage comes looking for the young apprentice and political chaos ensues. Voila! An adventure that gives the feel of a well-thought out world with minimal work.

 

[Greatwyrm]

FWIW, the more you deviate from the norm, the more you need to prepare. If your concept is pretty simple, you can wing it more. If its pretty far out, do more homework and it'll seem more 'real'.

 

[Starglim]

For the first adventure, all you really need is a safe place to start, a dangerous place to end up, and some obstacles in between. I started one game with the name of a village, a range of hills, and a goblin outpost.

Once the players have tackled the first adventure, they'll most likely seek out civilisation to rest, spend their gold, restock and decide where to go next. This is where you need to develop the town to let them do those things. The name of the ruler or nation, and the direction of areas of relative danger (the borders of the nation as opposed to its heartland) will probably come up at this point.

They don't really need more until they are free enough of trouble to travel, and high enough level to affect the course of a region's history - say, 4th level. At that point you may want to develop a few adjoining nations and sketch out the biggest threat on a national scale, such as a humanoid horde or aggressive enemy nation.

 

[Bran Blackbyrd]

One problem I've had with my campaign world; working sequentially. I've got the outline for the story arc and that's great, but I always seem to come up with more material for things that won't happen for another 20 sessions.
Once you've plotted the major arc from A to Z, concentrate on points A-G. Put the rest in a drawer or something. Reference them if you need to visualize the arc as a whole then put them away again.
I have failed to do this and I'll tell you where it's gotten me; I have a ton of material regarding the mid to late game, and almost nothing that will help me write the next session. If you can't get to the next session then it doesn't matter how many epic battles and earth-shattering revelations you have planned for the players down the road.

The closer you stick to a "normal" D&D world, the easier you'll make it on yourself. This is especially true in regards to magic! If you goof around with magic or the way magic works you are inviting a world of hurt upon yourself. So, keep it simple if you aren't ready to tackle that particular juggernaut.

Make lists of names for: People, Cities and Locations (this includes geographical features like forests, oceans and rivers, etc.), Businesses, Organizations and Conveyances (like ships, boats, air-ships or whatever). You don't have to come up with backgrounds for them (though if inspiration strikes, feel free), just have them ready if you need a name.
Nothing taints a game like having to come up with a name for something on the spur of the moment and you blurt out something stupid. Your players will remember a silly name or a name that is easily subjected to innuendo and puns INSTANTLY and they will do it (intentionally or not) instead of remembering what you sweated over for hours.

A DM of mine once told us the NPC we were talking to was named Gael (pronounced Gay-El).
What do you suppose the focus of the conversation was for the next half hour?
That's right, Gael the Gay Elf.
He also named a kingdom Lorfensaurius (I don't remember the exact spelling, but that's close enough). No one cared why we were supposed to go to that kingdom, they only cared that it sounded like a breed of retarded dinosaur. We had some young players in that game too, which made it worse. He changed the name to Laustaurius or something, but that only made the old name stick out more and no one ever forgot it. Every time the new name was mentioned, a player said the old one.
In addition to helping you avoid those scenarios, having ready-made names makes it look like you really put some time and care into your world (one would hope), and your players will pick up on that, appreciate it and care about the world too (again, one would hope).
There's much more flavor in having your characters go to "The Laughing Lord", an inn which has a sign depicting a king laughing so hard he's falling out of his chair to spend the night than there is in staying at "The Town Inn" and it only takes a few seconds to come up with the name and descriptive bits.
This also helps the DM in the end, because players are more apt to roleplay without being pushed every step of the way if they have some idea of what's going on. A really good player will try to make do with what he's given, but a beginner or a shy player will find it much easier to roleplay if they are fed a few details and you roleplay too.
If you tell a player, "You're in a tavern.", they'll probably tell you, "I ask around for information about Uber-Villain."
If you tell a player, "You step into 'The Winning Hand', a tavern known for boisterous card games, and its rowdy but friendly customers. The barkeep gives you a friendly nod and says, 'What can I do for you?’ they might just say, "I approach the barkeep and say, 'A pitcher of ale for my friends and I, good sir. This establishment was recommended to us by a man traveling this way. I believe he said his name was Uber-something... maybe you've seen him...."

You never know. At any rate, a little bit of description goes a long way.

Oh, and make sure the players know that they don't have to speak in a stupid accent when they roleplay. The assumption that you have to try and speak in a faux-british, scottish, irish, or whatever accent (Hello to you UK EN-Worlders! ) in order to be in character has probably kept more shy people from trying to really roleplay than all of the anti-D&D press you've ever heard. If you're bold enough to ham it up without feeling like a moron, that's fine, but a lot of people feel stupid affecting an accent and they lock right up. After all, no one wants to feel stupid. That's more of a DMing rule in general, rather than a campaign creation tip, but it's free so...

 

[TerraDave]

I'll emphasize what TerraDave said. (i feel there should be an exclamation after your name, like TerraDave! is here to save the day!).

LOL...TerraDave, not TerraMouse (or would it be TerraMighty?)

 

[BiggusGeekus]

Start small and work out from there, if you do anything else you will go insane and die slowly in the rain, alone and unloved.

I'd suggest starting them out in a small villiage of 100 or so people. Keep the stakes low so you can raise them later.