Because your writing on your time, and it going to take a long time to finish, it can be easy to put off working on your novel, and in the end get little done.
What I find effective for myself is to set short term goals. I have a goal for most weeks, that I will get done with editing a certain section or write a certain number of scenes ect.
I also will have a goal for most days. For example as of the time I am writing this my goal for the day is to edit half one part (about an eighth or so) of my book with the edits from my latest round of alpha readers.
You won’t always make your goals, and that’s okay, but you need to try.
You also might need to set limits on how much you redo things. It is very easy to keep tweaking a section for much longer then it’s worth. During my first draft I made a rule to not go back and fix things unless they were something like proper nouns or numbers. More then that I let abide, and in the end I found it much easier to edit the whole thing when it was done. Sure I had a lot of problems, but they were easier to fix when I could see the whole picture.
It also helped my motivation to know I DID finish the first draft, I KNEW I could complete the book. Sure it may take a while but I was going to do it.
One of the things that Star Trek is famous for is having a black bridge officer, during the 60’s.
The future of in Star Trek was shown to be one post bigotry, post racism. The interesting thing is that they did not show this by bring it up, they did this by just letting it be.
They showed the crew, let everyone see that Uhura was black. It was not important enough to remark upon, the fact she was black was as unimportant as the fact she had black hair.
I am telling you this not only for the obvious but to show you that you don’t have to mention something explicitly to make a point with it. Making a big deal of something can in fact detract from it. For example if space travel was easy and common I might not make a big deal of going to orbit, the fact that I was going to orbit for lunch could be a good way to show that we are in the future, and how advanced things are (or how rich I was).
One of the biggest problems writers can have when starting out is to not have a real ending. By this I don’t just mean a novel that requires a sequel to finish telling the story (also a bad idea by the way) but a story with no real resolution.
You should resolve at least one major thread by the end of the book, if others are open that is fine, but you need to close at least one. In fact you SHOULD not close all of them. You want your book to feel organic, like the characters are acting and decided things, not that actions are happening and your characters just happen to be nearby. In real life you never reach a point where everything is resolved.
Think about the end of the World War Two, the war was over, and everything was much better. However it led to the cold war and a great shifting of power in the world. Nothing in real life ever just ends.
That said, you need to have enough resolution that the book feels over, even if the overall story is not.
This applies, in part, to minor threads as well. All the minor threads should move, they should be going somehwere, or they are not worth pagespace.
To keep things moving it helps to have goal posts, touchstones you can use to make sure you know should be happening when. For example:
Joe and Mary, meet and hate each other.
They admit they are very attracted to each other and have sex.
They start to live with each other after spending time together.
They get married.
The plot is always going somewhere, and you need to know three and four to write one. You need to know the end before the start can really work.
Now you may not know the end in the first draft, just don’t be afraid to go back and revise and you’ll be fine.
The way of the Pilgrim by Dickson is one of the few really good alien invasion stories I have read. It takes place years after the invasion is over. We were against an alien force VERY far beyond us, we were not able to put up any real fight (Think Aztecs verses the US marines of today).
There are two things that really make it stand out, the first the aliens are not just a little ahead of us. They are so far ahead of us that it could very well be possible for one of them with their weapons and gear to defeat the entire military might of the Earth by themselves with little effort.
This is a much more likely scenario then aliens attacking who are far enough ahead to come here, but not so far as to be unable to easily beat us. Think about what a modern air craft carrier could have done during world war two, and that was less then a century ago.
The other thing is that it builds up what would happen to us socially and psychologically during that situation. This is one of the reasons the book is as long as it is, and I feel the page space was well spent. The fact that we do not get a victory through military might or technology makes the ending that much better.