From 30 Days of Worldbuilding:
1. "Write down the snippets and images that you already know you want in your story."
2. "Next, ask yourself the hard questions 'What if?' What would that do to them? Would that change my plot?"
2a. "Drill down on the big things and the details, decide what would happen if they work one way vs. another."
What if? The idea here is to flesh out how the elements mentioned affect society.
I'm guessing "speculative element is magic. What I have so far, magic comes from Dragons. Magic is controlled by magic trees, and is driven away by technology like each is a magnet. Magic follows Ley lines and they are a cross between powerlines and forcefields, embodied in Dragons. Anyone can "do" magic and magic can be "put into anything." Magic became stronger as it was collapsed into Seekretya.
Ask yourself the hard what if. I don't know what that means. What if what? What if Ronald Reagan isn't actually dead, but is involved in a life commitment with Elvis, who also isn't dead, but living in a small cottage on the north side of the Confederacy of Liit? Obviously this isn't the kind of what if they're talking about.
When I did this for Heavy Magic I didn't ask what if, but instead did more fleshing out of the magic. I've been getting in such detail in each step that some of the following steps end up just being rehashes of earlier ones.
One thing I'm not really sure about, make that two, how exactly is magic applied; how are spells cast? The second one is, if anyone can do magic, and it's all around and very powerful, why doesn't everyone do magic? If everyone can do magic then what is life like?
I don't think I like the feel of everyone being able to do magic, more like 1 in 10 or 1 in 5 is better. So about one in each house or family. That seems ok. I think "doing" magic is so time consuming and exhausting, studying magic so extensive that each family can only support one magic user, and often whole villages get together and support a few magic users, some or all of which will be Wizards.
Does every magic user need to be a Wizard? No, I don't think so, but the professionals are.