The Catch all. The players has an item that others specifically want, an accident, they get sick, hearing a cry for help, accused incorrectly of a crime, and other randomish events.

Large Groups/ Societies/ Organizations/ or parts there of are in conflict with each other. Because this is occuring, the events of the plot occur.

Something new enters the picture which drives the characters or they are trying to solve a mystery of some sort. Could be a lost map, find the murderer, a search for something, a secret revealed (or still hidden).

It is a characters obligation to their station/ social class/ or organization to become involved with the plot.

The event is a catalyst for the plot. It could be a holiday, tournament, regime change or even two locals going at it that begins the plot and brings the characters in.

A character is hired to do something. That something may or may not be what the plot is about but is what brings them into it.

Some magical/ spiritual/ paranormal event has occured. That is what brings the character into the situation.

The natural world through weather, earthquake, animal, plant, or disease brings a crisis into the world for the players.

The character is travelling and has that has brought the character into the plot.

Far reaching, fully fleshed out, multiple levels of storylines, locations, npcs and encounters all wrapped up in an organized fashion. Non-Linear. Requirements will most likely drive a new game.

Small, but interesting interaction that doesn't take a lot of time and does not cause any deviation from current game events. QUick game entertainment.

Many game requirements using specific events and or locations to drive a large complex storyline. Linear and non-linear. A large long reaching set of events that can still be used in current game, but also might drive a new game.

A plot that is starting to get more complex with many things coming together and overlapping. Still doesn't have too many specific requirements so that it can still be used easily. Linear or non-linear. More complex set of game events but still useable in current game.

Another small, but interesting, diversion that may take the players some time, but will inevitably return them back to the current game events. Small game diversion.

Fully contained, solid plot that has story driving content with a set beginning and end. Doesn't require to many specific things remaining easy to put in anywhere. Linear in nature. Solid, simple event for current game.