The Plot Hook

How to get the adventure started.
I have been reading one of my favorite RPG books, the Burning Wheel, and thinking about how I would like to run that system. In the Burning Wheel the referee pitches a situation idea to the prospective players prior to even setting up the game. My thoughts on this topic started with the Burning Wheel, but they are applicable to most any system as a way to begin planning an adventure.
In the Burning Wheel the situation is discussed first so the players have a better idea just how to build characters (in game terms this is "burning" your PC) to better fit the specific situation. The Burning Wheel campaign ends naturally when the situation seems resolved.
The Burning Wheel does not include a setting, but it is set up to facilitate the traditional Tolkienesque milieu. Life paths include humans based on medieval European history and elves, orcs and dwarves are possible PCs. In the Character Burner section of the Burning Wheel there are life paths specifically tailored for those character types. Beliefs, Instincts and Talents play a significant part in earning character experience in the Burning Wheel and knowing the situation ahead of character generation can help make the system work smoothly.
Places of mystery, rumors of villainous activity, opportunity comes knocking, these are all ways to start off a game using any system. For the Burning Wheel my first thought is to ask players to burn characters who are all presently in a certain small town. The town is troubled because conflict is opportunity. The current conflict started when the new mayor began bullying the populace. He recruited thugs to enforce his will and levied taxes to support his administration. He is currently looking for a new "wife" to replace the one he set aside when he became mayor. His eye has fallen on a young girl who is quite frightened by the prospect of becoming Mrs. Mayor.
I will ask the players to create characters who have some investment in the town. They should have established relationships with a few named residents and a belief about the current situation. This engages the player characters with both the milieu and the conflict and gives the referee the opportunity to make the game about something the characters care about. Engaging players is what the Burning Wheel is all about. It is also a great way to enjoy most any role-playing game.
I will provide the players with a short list of townsfolk they might want to include among the people they have contacts with, such as the young maiden being courted by the mayor, her family, the mayor's estranged wife, town guardsman, merchant or guild (maybe even the mayor, himself?).
Just what-all the mayor has his sticky fingers into can be adjusted based on the interests the players express through character generation. It's always a good idea to connect the setting with the characters and the Burning Wheel practically makes this a must. When the author says something like the wheel revolves around the characters he is referring to the characters being the actors who create the story that develops from play. As referee, making the game about the characters should be a goal.
Whether the situation is "There is this hole in the ground rumored to house monsters who guard treasure." or "There are these cultists hell-bent on destroying the world." or even "Here you sit in a crowded tavern down to your last copper..." a situation is an opportunity for play. It is the responsibility of the referee to set an interesting situation so the players can take some heroic action through their characters and that is how the game often begins.