Preparing a Sandbox World

[Wacky89]

Okay so i'm starting up a sandbox world located in Faerun, playing dnd 3.5.
I'm new as a DM, i did do some dm'ing before but it was mainly dungeoncrawl or heavy combat campaigns

What do i need to prepare to start up?
I know i need a random encounter table
Maybe some quests for them to do?
I need a location, I'm still looking at the map to find a good location.
What else do I need?

[Seppo87]

Forces that act independently from the PCs that will generate interesting stuff that you can make happen when appropriate.
I.E.

-At some point a dragon goes on a rampage somewhere. You know why, the PCs don't. They may or may not do something about it. If they ignore it, the dragon will achieve its purpose and will reappear later, or something like that. It's their choice however, the PCs may even ally with the dragon. Just make sure you know what the dragon wants and how he plans to obtain it, and then just make stuff happen as planned unless players get involved.

-An old rivalry between two kingdoms is about to erupt into a war when a noble is assassinated. You know the reasons and the natural outcome of this (probably: the good guys lose) Suppose the PCs decide they do not care, you have many options here. Maybe a group of NPCs will take the job and save the day, unveiling the evil plot. They will become famous. Maybe the PCs will hear about them or even meet them later.
Or perhaps the good kingdom really is doomed and the world will be reshaped i.e. some stuff that you could buy in stores is no longer being exported because of the war. Players will see stuff having real consequences. (this is not a punishment for not doing something. Good things can happen as well, just make sure they get a feeling that the world is going somewhere and behaving dynamically)

-The daughter of the innkeeper is a very anxious girl. She will be fascinated by brave and strong adventurers.
Perhaps after meeting the PCs she will try to become an adventurer herself.
You can place this kind of detail everywhere, you don't have to choose in advance where this inn is located. If it's interesting, just make it happen wherever.
Maybe she will survive. Maybe she will die. Maybe a player will get Leadership and guess who's the cohort.

-Dwarves need help freeing the mine from monsters. The mineral extracted is crucial for XYZ reason. They get the mineral, XYZ happens. They lose the mine, XYZ doesn't happen.
Ask yourself: is XYZ interesting? Can it be tied to other things going on with my world? How and when, if ever, will this change things around the playing characters?

also,
Ideas from your players. Give them the power to partially shape the world.
"Where are you from? Oh so that village which was not on the maps, well, now it is. Ok. Who are the important npcs? Ok. How does this place interact with the world? Very well"

You can use this information to produce player-based plot hooks

[Nuada99]

I think it's also helpful to have at least a small stock of useful NPC's. Not talking about villains here, but people the PC's would interact with more than once. For example:

- That scruffy weasel-guy who can sell anything the PC's find, even if they "found" it in someone else's house (fixer)
- That noblewoman who likes to gossip about the tawdry goings-on in the court (assuming your PC's ever cavort with the high and mighty)
- The head of the merchant's guild who often has missions for aspiring adventurers
- The local sergeant of the town watch who is gruff, but fair.
- A corrupt church official who is too important to kill, but too corrupt to ignore.

etc. You get the idea. These sorts of NPC's really make the place feel more real. All that said, the advice by Seppo87 is truly great. I'm glad I read it.

Also, as Seppo mentioned, don't be afraid to let your players contribute NPC's, interesting places, and other details to your world. It's an easy way to make them feel more connected, and also help flesh out your world.

[Toilet Cobra]

With a sandbox game, I find it useful to look ahead with a series of simple IF/THEN statements.

Ex: The players are currently in City A. City A is run by a cruel and corrupt elite class. IF the players do nothing about the corruption, THEN things will get progressively worse, until a revolution occurs in twelve months' time.

The players can notice the progressive deterioration of the city as they go about their business. What makes it a sandbox game is that they can ignore these events entirely, or at any point they can jump in and fight the corruption, work to prop up the nobles, or pursue their own agenda. And you can imagine an IF/THEN for any city, group, or person in your world. IF nobody kills the dire rats in the basement of the Tipsy Troll Inn, THEN the barkeep eventually gets fed up, bludgeons all the rats with a mallet, and becomes a first-level fighter.

[Gildedragon]

To reduce legwork on your end the speak authoritatively rules found here:
http://www.giantitp.com/forums/showthread.php?201014-3-5-Remix-The-joy-of-skills!

A lazy DM'S best friend: offsource the work to the PCs
That way they might hint quite a lot at you as to what they want to find and do

[Florian]

Okay so i'm starting up a sandbox world located in Faerun, playing dnd 3.5.
I'm new as a DM, i did do some dm'ing before but it was mainly dungeoncrawl or heavy combat campaigns

What do i need to prepare to start up?
I know i need a random encounter table
Maybe some quests for them to do?
I need a location, I'm still looking at the map to find a good location.
What else do I need?

Most important part: Motivation.

What you seek is a safe spot on a wild and untamed frontier. There must be danger and adventure and no higher authority there that could reasonably deal with that stuff. The characters must be the real heroes here and what they accomplish must count something.

Second thing is plot hooks. Stuff that is known, local legend, recent happenings, gossip and rumors.
That doesn´t have to be fully fleshed out adventures. Just general things like:
- We fear the Orcs are going to raid us soon, we heard there´s a now Warlord....
- Ever heard the story of the Witchblade? That legendary Bladedancer that died fighting those giant back then...

Third are power structures the player can take a liking in and potentially care for:
- There´s unrest in (Town). It´s the (Free Citizens) going up against the (Noble Families)....

Fourth: Actions have consequences. Keep track of all that stuff. They pursued the legendary sword instead of stopping the orc horde? Well...

Ok, I´ve not had anything to do with the Realms for a long time, but if I remember correctly, look at the Sword Cost and Silver Marches for suitable locations. Avoid metropolises like Neverwinter and Waterdeep.

[WindStruck]

I think it's a good idea to first think of a general area you intend the game to be in. Then have an idea of the Major NPCs, faces, and events within that area. Stop there.

Why? Because it's a sandbox game. And seeing as players can do virtually anything, especially things that are totally out of the blue you would not expect, there's no point trying to design a bunch of NPCs and non-essential locations. Even the "essentials" you describe could be entirely missed. The most important thing in a sandbox setting is to be able to make up content on the fly.