How to keep readers reading

Best advice for novel writers: READ MORE

It's vital that writers to understand the conventions that readers are familiar with, in order to avoid cliche or worse: incoherence. 

Breaking the rules invites ambiguity

So what are the rules about keeping readers motivated to read on?

Plot comes first. However convoluted the plot, it can fit into one sentence. 
Tell your friends no more than that one sentence and remind yourself of it every day.
Keeping the plot sentence in mind helps writers write a continuous story and also helps agents and readers decide whether to buy. Knowing the plot keeps you away from sub-plots and irrelevant episodes.

Beware any changes in plot after your first draft; every change will have consequences on each page which will be tiresome to correct. By all means change the characters' names, gender, dialogue as much as you like but plot is sacred from the start.
Plot provides the motivation for your main character and it changes in a special way through the story. and yes, keep to one main charcater and maintain their point of view throughout.
[established writers ignore this but for first novels a rambling point of view puts people off] 

So what is a plot?

Stories open with stasis: the kingdom is in neglect, doom-laden, or everything seems fine but the king is ageing, rumours of dragons abound. Whether you start with action or dialogue, your novel informs the reader of the characters, the place and time and underlying this: the genre [thriller, mystery, horror, historical, romance] Concentrate on your favourite examples of your favourite genre and you will have a repertoire of clever plot twists. 
You can introduce the rules of your fictional world through action, narration or dialogue. If there is magic or paranormal events they are bound by certain rules such as: having a wand made of a particular wood, or having telepathy only with those you love.
Then comes the trigger, the call to action for our hero or heroine. A significant event brings the character to life [eg a beautiful princess is entranced and sleeps for a hundred years]
Ther character sets out on a quest. The object of his quest is often a symbol rather than anything especially valuable. Readers are asked to suspend disbelief, the wrtiter and the character believe that only this one object will bring happiness, relief, safety or survival.
Surprises happen. 
A good writer constantly reaffirms and contradicts readers' expectations. Stories that are entirely predicatable are boring so plan a surprise for every chapter ending. A surprise is an unexpected plausible obstacle or help to the character's quest. She meets antagonists and protagonists, a wise woman or a cruel tyrant.
Then she is faced with a critical choice which demonstartes free will. Things could go either way. She decides to follow a path which is fraught with danger.
This leads to the climax in which she confronts her greatest adversary: time, dragons, a torturer or an arranged marriage and a tense conflict plays out resulting in a reversal: now the character has changed in some way, become more resourceful or lost the battle and accepts defeat. Finally we have the resolution: the new stasis in which the world of the novel is altered following the climax.
So what has kept the reader turning each page?

Surprises and rising stakes. As the story proceeds the character rsks more and more until she stakes her whole life on the outcome. 

I haven't made these rules up, if they sound dogmatic, they can be traced in most films and books and talked about in plot advice to authors since the time of the Greeks. 

In my view, plot awareness is the author's best friend.