I was first introduced to this idea by the brilliant and gracious William Stoddard via the Pyramid discussion boards. Rather than having the GM dictate game that might not get player buy-in or having the players force settings on a GM a Campaign Prospectus provides a large group of players a list of possible games on which to vote. Once they vote the GM sorts them into campaigns based on stated desires and preferences, thus making sure everyone has bought into the campaign concept. Doing so solves a huge raft of problems and it also spurs the GM to come up with more –and quite probably more offbeat – campaign ideas then they would have done otherwise.
Much of this web sites eventual content comes from games pitched in prospectuses that I either got a chance to run or had to write up to get the idea out of my head and onto paper.
*Direction, Objectives, Strategy and Tactics*
One question of campaign design is who is determining the focus: is it the GM or players?
A GM-Directed game is one where the GM determines the focus. Imagine a Star Trek game in which a federation starship enters a system in which something strange is going on and the PCs deal with it because they have to (the problem immobilized the ship), they want to (it plays to PC interests), they know they need to in character (colonists will die if they don't) or out of character ("Hey guys, if you don't do this, we ain't got no plot!").
A Player-directed game is one where the GM provokes reactions from the PCs, but the players are the ones who set the course. Imagine a Star Trek game in which a Ferrengi Trading vessel takes off from DS9 with a list of possible cargo ports… but they might decide to go pirate or try to mine deuterium from a star. GM can react with suitable challenges but the majority of the sessions will be based on player decisions.
Within these definitions Direction exists is on a continuum based on who's responsible for deciding objectives, strategies (how to reach the objective) & tactics (how to complete the strategies).
In the most GM-driven game – usually a convention or other pre-gen scenario –the GM controls two of the three and strongly influences the third (objective: get the ruby of Achaok; all strategies involve going into that dungeon; the tactics will be based on abilities of the pregen PCs) leaving players with a limited array of tactics to implement the allowed strategies through the setting & genre. A ‘traditional dungeon crawl’ game is similar but with with player generated characters Players have more control because they are free to solve each problem between them and the objective as they wish, even if the GM identified it and genre and character creation rules served as limits on their tactical choices. For example, if they don't kill the guardian hydra they can't get through that door to the Ruby of Achaok. The character creation rules stressed armored clerics, mightly-thewed barbarians and fire-invoking wizards, so strategies other than killing the hydra are non-optimal but not impossible, and the tactics will weigh heavily towards direct confrontation.
This sort of game can be fun because it is easy and fun. Everyone knows what they're supposed to be doing, and the GM can prep knowing no one will try anything outside the proscribed strategy and tactics (such as "we leave to find the best hydra-slayer in the land, and pay him with a share of the copper we're mining from the vein we found on level two!"). Discussion of tactics is usually had in play and can count as spotlight time - team-oriented groups will pick tactics that distribute spotlight equitably.
In other games the GM & genre exert less strategic control. The GM still sets the objective but leaves players to decide how to reach it, and the player characters have a less constrained set of tactics. For example, the player characters are offered a reward by the princess for getting the Ruby of Achaok, but in this campaign the character creation system is wide open (say GURPS rather than D&D), so the PCs instead consist of a gnomish alchemist, the owner of a small dwarvish mining concern and a recently retired ‘ambassador without portfolio’. The objective is identical, the strategies are highly likely to still involve entering the mine, but it’s very likely that the individual strategies and tactics will be wildly different.
In this sort of game player developed strategies are best done at the end of a session or between sessions so the GM has time to determine how the strategy will work. This means discussions of strategies are only limelight time if the GM has to provide information that the PCs would already know but the players don't. If the PCs have to acquire that information, that becomes the cause for a new set of tactics.
Then there are games where the GM sets up the world & the genre, but the players set the objective & tactics. For example: "OK, we're playing _Mage_ and the Technocracy has near-total domination of the world. What do you do?" This is a very different question from "How do you stop them?" With the latter, the GM set the objective: the PCs should stop the Technocracy. In the former, the players might flee into the Umbra, join them and aid their cause, build a sanctuary against them, try to reform them via debate or fiddle while Rome burns. Discussions of objectives should clearly be group spotlight time, as the Players and/or PCs must discuss what they intend to do and the GM must be aware of that from the outset. These can be tricky because some players flounder without a clear objective; to be fair however, some players thrive on it and bristle at games where the GM asserts more control.
Finally, there are the games like Prime Time Adventures, where the GM doesn't have significant extra control over the setting. The players develop the setting, objectives, strategies and tactics with the GM being nothing but an equal partner.
Most of the campaigns you’ll find here are of the first two sorts – I will recommend more control the more the campaign is trying to emulate a specific source material – with some in the third. I doubt there will be any of the fourth category, since those sorts of games are almost all ideas on how to develop campaign concepts and set of mechanics to run them. Those are great for that, but run counter to me telling you my own clever ideas. I am a fan of campaign ideas that have clear if unusual strategies and tactics because they will feel new and interesting without leaving the players wondering what they’re meant to be doing.