Your plot can be either event-driven or character-driven, though these two plot engines may run in tandem with now one, now the other, taking the strain of pushing the story forward.
Tom Monteleone in The Complete Idiot’s Guide to Writing a Novel neatly sums up the basis of all plots as being either:
Man against society
Man against Man
Man against himself
Man against nature
The writer’s job is to mix all these elements above to make a truly great story but, one element is vital; the truly great story will have plenty of complications. This very often means that when the situation is looking bad for the protagonist the writer’s job is to make that situation worse. Think of Richard Hannay in The 39 Steps when not only has he a dead body in his flat, but he then decides to let the police make of it what they will and try to solve the mystery behind the murder himself. This decision, of course, leads the police think he is the murderer. This leaves Hannay to clear his name and save the country from the enemy all in the space of 124 pages.
It is these complications which make the story interesting but which also lead to the resolution in which the protagonist has changed in their outlook or material situation.
Think also of pacing your novel, making sure there are plenty of high-octane moments interspersed with quieter scenes where the writer can clear up some loose ends and set up some further complication down the line. That said, every scene should be deepening characterisation, mood, explaining background or building the reader’s understanding of the protagonist’s situation.
When writing your novel think of an end point you want reach and point your reader in the direction but once you have the reader thinking they know how the direction of the story you add in your complication and change that direction. These change points help you pace your novel and keep the reader guessing whether the obvious ending will be achieved. Change points can be of the following type:
Reverses – when everything seems to be going well the writer throws a spanner in the works.
Discoveries – where the characters find out something unexpected.
Recognition – when the protagonist realises they should have guessed the thing the reader suspected all along.
Remember, that though the writer’s job is to “make ’em wait!” all the actions in the novel should be logical to the story line so far. This is a mixture of making the outcome of the story believable and the protagonist’s actions, rooted in their behaviour traits, also believable.
One good source of advice available via a web search is the Lester Dent Plot Formula. These words of wisdom from one of the masters of pulp fiction gives a line-by-line break down of how to write a 6,000 word story, but is useful and adaptable to stories of any length.