I recently tweeted a discovery I'd made about revision:
The revision process seems largely to be about steadily transforming the protagonist from passive observer to active agent.— Ann Gelder (@AnnBGelder) September 1, 2015
I would now add that this process also involves winnowing down the number of characters, so that fewer people take on more responsibilities. I find that after a first draft (or even several drafts), I often have two characters essentially performing the same function, and one of them is performing it less well--and doing nothing else constructive. Therefore I have to give one's duties over to the other, which a) gets rid of a boring character and b) creates a more interesting character out of the one remaining.
As you go through this process, think of yourself as the Bain Capital of fiction: swooping down on a perfectly nice, quiet but inefficient little novel, and ruthlessly getting rid of dead weight--who fortunately are not really people in your case. Presto: your novel is now leaner and more productive. Or, as Jeb Bush would have said, had he been an author instead of a really bad politician, everyone in your novel should be working more.