Update the campaign outline after each game session. Maintain a calendar and track the elapsed time. The key to developing a consistent campaign is to logically link the chain of events. This outline will provide for quick review of what has occurred and feeds into the future development of the campaign. Don't go over board with detailed. Keep the entries short and sweet.
Figure out what the villains will do next? What are their next steps? How will they advance their own agenda? Their plans do not necessarily involved the adventurers. How might the adventurers learn of it in time to oppose them?
Think ahead. When designing the current villain have the next foe in mind. No matter how dramatic the conclusion of the previous adventure the current antagonist is always an insignificant piece in a larger game. As the game progresses, the party will need to encounter more and more powerful opponents. In a sense being the hero is really an exercise in futility. For every opponent that is overcome there is always a new opponent waiting in the wings to take their place.
Their will always be villains to oppose and there will always be plots contained within plots, contained within plots, and so on. The campaign outline is a useful tool to help keep the plots straight. The good news is that the plot doesn't have to be designed in advance. As long as there is a general theme for the campaign then events can be expanded in any direction. A particular plot for an adventure shouldn't involve more than what might be seen in a typical television episode.
