One of the difficult areas for me as a first time writer was getting my head around fleshing out the minor characters. I mean, in my head, the story of Salvation is about Alex vs The Khaos Lord, so everyone else is just padding, right?
This is a tricky one - of course the story needs to be focused on a main character (unless you are going down the current in vogue route of copying the Song of Fire & Ice format and having numerous angles, if so good luck!) but you need others to step in from time to time, take the limelight and break the story up, adding depth. If your side characters just turn up and act as padding then the reader won't care about them, and frankly they become boring. Likewise, you don't want your side characters to be so great that they make the main character stale, and the reader wants to read more about them than the story you have written.
In my view it's hard to say who counts as major and who is minor. Think of Harry Potter - Harry is the hero and it's his story, but would you say Ron, Hermione or Gandalf are minor? Of course not. Same as LOTR - Sam, Gandelf & Aragorn all have significant parts, and importantly, have been developed to make the reader connect with them.
When starting out to write your fantasy or SciFi story, or for that matter anything in the fiction realm, spend time creating a catalogue of characters to fill your new world. You will be surprised the variety you will come up with, and if you do it well, you will identify new paths to take your story down that you hadn't even considered.
The trick is to keep focus on your main character, but have 3 or 4 detailed side characters who add variety as the story goes along. In Salvation I consider these characters to be Kastral, Haswell and even Max to a certain degree. If done well these characters will only have their surface scratched in your novel, making the reader want to know more about them and their exploits, thus leaving you with plenty of material to explore in future novels or spinoffs!
Remember your novel, even if just about one persons journey, is never about one person. Make everyone the reader comes across come to life!