I'm hopefully planning on writing a novel series and know the overall plot arc for the first book: "Layne Campbell knew very well that his family was different from others. Having had secrets hid from him his entire life, the truth is revealed in the most unpredictable of ways. Finding out he was the reincarnate of one of the old wolf gods was not on his to-do list. Finding out his true intent in this world, to start the restoration of peace to the species and relight the faith of the old gods, turns his world upside down. However, those with other intentions wish to stop this progress, including his own father" (and briefly some for the others too) However, I'm following this rough plan for writing the first novel draft and have only got 3 points so far: Act 1 Introduction to the protagonist's world - Layne and his sister moved to yet another new school due to their father’s ‘work’. Call to action Crossing the threshold Act 2 Mentor teaches the lead - Layne gets shown an old book and learns further of The Children of Amaris. First challenge Temptation Dark moment Act 3 Final Conflict Return home - Arrives home with the knowledge of what he has to do next: try and find his fellow reincarnates." Does anyone have any further ideas?
Have you tried just writing some free-floating scenes? They don't necessarily have to be things you will end up using but they might spark some ideas. I have a few questions, you might already have answers, which will hopefully help flesh it out a bit, or if not they are things to think about: Who are these others with other intentions? How do they wish to stop him? Why? What is his sister's role? Who is his mentor and what is their story? How much of a back story do we get on the father? Why does the species need restoring, what happened? How much do you know about what the temptation and final conflict (and the other sections you've mentioned) will be (as in do you know any of the specifics)? Is the story going to work as a stand-alone with more in the series if it goes well, or is it going to be left on a cliff-hanger with a definite sequel? I know you mention the ending is Layne deciding to find others, but is it possible you might condense it into one book? Are there going to be any side-stories going on? I think you just need to keep asking questions about your characters, what they want and play around with putting them in different situations, even if they don't go in the book. Also are there any particular themes or side stories you want to explore - do you want a big betrayal, a romance, a redemption arc. You might not know this to begin with, it might develop as you get to know your characters and your story, and they have to be there for a reason so they don't feel tacked on just to pad it out. Personally, I find romances can be particularly frustrating for this (if done badly!) where people feel the need to force a romance in that doesn't seem real at all. But of course, every writer has their own way of doing things so just go with whatever works for you good luck!
