There's been a lot of talk about Sandbox play on RPG forums and blogs in the last year -- and not just among old school players. In its pure form a Sandbox GM sets up a (usually small to start with) area of the world with encounters, dungeons, and NPCs of varying power levels. The player's characters start in the area and can do whatever they want to do. If they hear rumors of a dungeon, they can find it and start to explore it. If they are more interesting in following up a rumor of an old red dragon with a lot of treasure who lives in a large cave in the solitary mountain to the west, they can head off over there instead even if they are only first level. The world exists as it is and adventures are not adjusted for the current power of the party. Instead the players are expected to gather information, scout things out and decide what they are able to take on. One of the best descriptions of a sandbox campaign are the West Marches series of posts on ars ludi.
A number of people have tried Sandbox games, some with good success, others with poor success. Often poor success seems to be blamed on poor Sandbox design or players who are not used to having to find their own adventures and instead just mill around doing nothing and get very bored. I've ran Sandbox style campaigns since I started playing in the 1970s. Sandboxes are the only type of long campaign I run. So I'm going to give a bit of advice on how to set up a Sandbox campaign, how to get it started and how to keep it running. However, I'm not going to repeat a lot of advice I've seen elsewhere so go read what others have to say as well.
Setting Up a Sandbox: There is quite a bit of good advice on this already on the net. However, one important suggestion I haven't seen discussed much is what makes a good base town for the start of the campaign. A small village will not do. You need a minimum of a small town so there is enough there to keep the campaign going. It's tempting to make you base town out it the boonies and off the beaten track, but that's generally not a good idea. You want a living town with NPCs arriving, leaving, and just passing through regularly.
Out on the frontier where there is lots of adventure is fine, but put the town on an active trade route. Even if caravans only come through once or twice a month, that provides the area with a steady stream of "new stuff": troublemakers passing through, people arriving to go adventuring, merchants to attract bandits, new people moving to the area, a way for people to easily leave the area, etc. When I design a base town for a frontier sandbox, I usually keep Dodge City from the old TV series Gunsmoke in mind. Dodge City was small, but active, and a center of trade for its area. Things happened there because there were always people arriving to keep things happening. That's what is needed in a sandbox as well as this will help keep the area fresh and interesting.
Don't begrude the time it takes to develop your base town. After all, unlike encounter areas, the town will be used over and over again. A number of well-developed town NPCS will provide the PCs with friends, enemies, rivals, henchmen, and many adventure hooks.
Patrons: Chances are your players are not used to creating their own adventures in a sandbox. The common style of gaming these days is a preplotted "adventure path" that the players are expected to follow. Often players used to that seem lost when their new characters are dropped into a sandbox world. Always have a few patrons with missions they need to hire adventurers for. These usually aren't world-shattering quests or long running plots, but simple things like guarding a caravan encampment or killing some nasty creature that has been killing livestock. One fun way to introduce players who have no idea what to do in a sandbox to the dungeon is to have their new characters hired to aid a couple of locals on a minor dungeon expedition. Chances are they'll treat their own hirelings better for the experience. It's a good idea to have several patrons ready in case the players aren't interested in the first or second offer. Even if your players jump right in and find their own adventurers, patrons can be useful at any time to provide new possibilities and choices.
Minor Plots: I'm not a sandbox purist. I think it is fine to have a number of background plots going on in the area and to allow the PCs to become involved in them if they wish. For example, in one campaign I ran, one of the NPCs was the bastard son of the former baron. The baron and his family had been killed in a orc raid some years earlier and a wealthy merchant had just assumed his place and used it to increase his wealth. The bastard son wanted to depose the merchant. The merchant "baron" was a thorn in the PCs side. The bastard son and the PC eventually met and the PCs decided to support the son and help him take power. This decision kicked off over six weeks of adventures that ran more like an adventure path than a sandbox but it worked fine. Things like this can make a sandbox more interesting -- but the choice to become involved and on which side should always be the players'.
More to follow.