I am writing a series and need help creating a name for them. An example of what I am looking for would be something like Cassandra Claire's Mortal Instruments or Christopher Paolini's Inheritance Cycle. My series is about the conflict between angels and demons and breaking the forged stereotypes about them. A young girl is abruptly thrust into this world when a demon who is illegally trying to earn wings, throws her life off balance and returns a year later needing her help to complete his search. She will learn that demons are not the monsters we think and angels are not the flawless creatures we see them as. She becomes wrapped up in a feud much larger than herself as the war between the world above and the one below enters her life and she discovers that the stories are always written by the victor, but the victor is not always the rightful hero.
I firmly believe that you should use a working title while you write and only try to find the publication title when writing and revisions are completely done.
Usually the title to a popular novel is decided by the publisher anyway. The title is part of the marketing and tuned to your target audience. If you write popular fiction, leave finding the right title to the marketing department of your publisher.
If you write literary fiction, you should still wait until you know what your story will be. While you write, you don't know yet how the story will evolve, and any title you try to give prematurely might not fit the final form.
I have taken many of my titles from the final sentences of my (literary, not popular) works. Writing the ending, I realized what I was writing about.
An approach recommended for popular fiction is to write a log line and condense that further into a title. (The purpose of the log line is the elevator pitch. See How to distill a plot into a logline?)
After a quick google search I found this website with tips on how to get started on creating name ideas for a book. Also, you could name your book after a key theme in your book i.e demon wings as the story centers around the demon who wants to earn his wings.
I find that book and essay titles come to me after writing a first draft and picking out themes that run through the book and playing around with words related to the theme. Maybe try putting related words into a hat and picking a few out at random to create a combination until you find one you like? I can't tell you what to name your story. Just give you advice, and there is plenty of it on google.
The format would matter first and foremost. Is this a series of books ala Harry Potter...or something "serialized" where the reader only is given the story one bit at a time over time? For extended novels I think a dramatic title is warranted say...."the Dark and the Damned" or "The Wizened and the Wicked." For something serialized you would want something brief...preferably a single word say "Tartus" or "Black Anthem" and then "rote" from there. Since the Battle between Good and Evil never ends there really is no "end" to the amount of story to be told and being it is told purely through the Mind's Eye I would say just write and then see if a title jumps out at you.
Since your book is about a young girl coming to understand the world they way it is (which sounds much like a coming-of-age story for a teen or pre-teen, or perhaps a coming-to-adulthood story for an MC in their 20's); I suggest you focus on a metaphor for learning or transition. The Twilight series is for a character metaphorically transitioning (from girl to a woman in love) and invokes a physical transition that was particularly apt for a vampire story.
Your story seems to be an education/transition story also (no problem, a million stories are, including my own). Key words are Understanding, Awakening, Education, Discovery, and so on. Seasonal transitions work, Springtime, Fall, Winter. Negative transitions: Destruction, War, Death. Positive transitions: Birth, Redemption.
Look for poetic and interesting words to talk about transition that also resonate with some element of your story. I am not making specific suggestions, this site is not for telling you what to write, but how to write. So there is a compass direction for you, a way to think about your series title.