So you have a plan, a draft, or even something you're really to call a novel. Before you put it out there, you'll need to take a hard and honest look at chapter, every scene, every word or it, with a distant, honest eye. One of the key factors you'll need to take a look at is the story's protagonist. Ask yourself the following questions to see if you're got the right hero for the job.
1. Does this character make an interesting entrance? The first time the reader meets her, is she showing some relatable/admirable quality, initiating or reacting to a situation in a provocative or relatable way? If your protagonist is sitting around thinking about how he/she got to that point in Chapter One, consider scrapping it (as a reader, I'm beggin' you) and starting with Chapter Two, feeding in only the tiniest splinters of backstory as necessary.
2. Is the character sympathetic on some level? Even the anti-hero might love his mother, worry about his carbon footprint, or slam on his brakes (or his way to a bank heist) for a mama duck and her ducklings crossing the street. Or maybe she simply expresses her wicked thoughts with such panache, honesty, or humor that we laugh in recognition. The only thing less forgivable than an unlikeable character is one that's so bland he/she vanishes against the scenery like a chameleon, so make sure we'll at the very least remember this character as we continue reading.
3. Does the character have agency throughout the story? Does she make things happen rather than simply having things happening to her? One of my pet peeves is what I call "dust mote characters," who simply float through the plot, buffeted by every puff of air (and usually whining about it.) If your character starts out passive, at least show signs that he/she has the potential to make a change.
One of the reasons, in my opinion, that Harry Potter has been so wildly popular is because rather that spending all his time angsting about his dead parents and mean aunt and uncle, he boldy and actively sets out to change things, even when it's risky (exhibiting qualities people look for in leaders.) Although the Twilight Saga, on the other hand, is a very successful series and has other good qualities, I was very annoyed by the character of Bella, who seemed to be much more reactive than active (at least in the first book, which was as far as I got in the series.) Characters should have more to do in the story than observe change and be rescued.
In my opinion, truly great books and series have truly memorable, dynamic protagonists. If you have a really good one, the reader will forgive bland settings, clunky prose, and plot holes you can drive a truck through. If you don't, even the most fascinating backdrop, cleverest writing, and most intricate story may not be enough to save yours.