I'll start with what went right. This isn't so much about the specifics of the story as it is about my writing process in general.
Developed Character Backgrounds Beforehand
For every major character, I made a chart like the one below. The information in these charts is out-of-date, poorly thought-out, and mostly never used, but if I didn't do it then every character would have been much flatter than they are. Knowing who the character is supposed to be, and used to be, helps when I'm writing and thinking to myself, "What would they do here?"
Random Passages
Before I started officially writing the manuscript, there were a number of scenes that seemed clear in my head. Often they were the ones that excited me most (my candy bar scenes), though sometimes they were scenes from a character's past, or scenes from a future book that may never be written.
Whenever I got stuck in my outline, or I got bored of the story or some character, I'd go write one of these scenes in a file called "Random Passages," prefixed with some note about the context of the scene. For Travelers, I wrote 9 such scenes over the course of the novel. Six of them ended up in the novel. Four of those were rewritten to the point of being unrecognizable (and one of the remaining 2 "scenes" was just a line of dialogue, three sentences long).
Even though they were almost never used as-is, writing these scenes kept me interested in the story and gave me a place to play with the characters before they were "committed" in the story. I read the scenes now and groan because they're bad and make no sense to the story anymore, but I also read them with fondness because I remember how much I enjoyed writing them.
Microsoft Word's Document Map Feature
I learned this during my life at Black Isle. Here's a quick run-down of the feature.
I didn't use the document map for an outline, though. The top-level headings were my chapters, and the sub-headings were the first lines of my scenes. It worked amazingly well to keep me organized and to remember where everything was.
Word Count Statistics
Most authors I've heard of keep word count statistics. I love statistics anyway, so for me, seeing my word count increase and dates of how long it took me to write a chapter kept me going. One of the things that motivated me to finish chapters was that I knew I got to update my stats file when it was done. It's geeky, but it worked.
Alpha and Beta Readers
Beta readers are the folks who read your manuscript before it gets sent out. For some authors, they read it when the draft is finished, for others they read it as each chapter is done. I have both, and call the former my beta readers and the latter, alpha.
For me, I had one alpha reader - my wife. She was both my encouragement and my insurance that I was on the right track. My beta readers were immeasurably helpful as well (in particular because my wife is not a sci-fi reader), but I don't think I would've gotten to the beta stage at all if I didn't have an alpha reader to push me through.