Todays installment is really more of a general writing tip, but it certainly applies to games as well:
The way to finish a game/scenario/expansion/product/thing is to start writing it and the way to start writing it is by typing on your keyboard (or other input method).
Don't get me wrong there is a lot that plays into game design: Testing, figuring out math, throwing out ideas that turn out to be bad, maybe some talking to players, research etc. But at the core of producing any written work is of course the writing.
Writing can seem overwhelming, especially when you look towards the end result. How big of a book are you looking to produce?
Renegade Scout was about 62k words. Five Men in Normandy is currently about 24k. A little 3 page Patreon piece I did a few months ago ended up at 831 words.
Let's say you want something in the mid-range: A comprehensive game but not excessively so. You decide to aim somewhere around 30k words. Maybe you think you have about 25k worth of things to say, but you want to add a bit of extra allowance if you come up with something really cool. Or you make some allowance you can use up for explanations, examples and designer notes. However you expect it to work out, the goal is about 30k.
Then you look at that number and say "I can't possibly do that, where would I find the time?".
As long as people have been writing books, people have been writing books about how to write books and a lot of that advice is applicable to game writing too. This article is about two techniques that I have found to be really helpful.
First I find it really difficult to think at the keyboard. If I already know roughly how something is supposed to look, I can grind out the text, but if I have to create mechanics from scratch I find myself stumbling a lot. It helps tremendously to prepare even a tiny bit in advance. For me this is usually just a notepad with hand scribbled notes. I might sketch out the core mechanic I have in mind and then once I put that down on the page with proper explanations, I am on the right path and now I can start filling in all the surrounding space.
I use keywords extensively. If I am working on the morale rules for something, I write down keywords and snippets. Sometimes they are short sentences, sometimes they are just a reminder. "-2 for outflanking" "Surrender?" "remove from play on second failure". Whatever gets you thinking. The same applies on a larger scale. The first thing i do when starting a project is always to name all the chapters and write in keywords for what I want to have in each chapter. If there is a "character creation" chapter and I want to have a "build your own class" option, I put a keyword for that. If you need help doing this, take a look at whatever rulebook you have lying around and look for what core features it (and any book) covers and what specific things it calls out.
When I sit down to write the next day or next week or next month, the keywords help act as a frame work and I can start filling things in. The more structure you build up, the easier it is to continue working on it because the range of possible choices narrows. A blank page can have anything on it. A page that says "squad based shooting" can only have a few things on it. Use that to your advantage.
It can feel extremely discouraging to realize you spent 30 minutes staring at the word processor without doing anything. Some writers say to just start writing anything and once you are "hot" then the material will flow. I sometimes work on a blog post or read over an old rules section to help get the engine running. You can try that as well.
Second I find that I benefit tremendously from scheduling. Obviously with a busy schedule you need to find the actual, physical time. I can't help you with that. However I usually set a word limit I want to hit every day. The number is not so important because once you are hot, you will almost certainly blow past it. However it can be very reassuring to be able to halt if you are feeling worn out that day. What should the word count be? That mostly depends on you. If you can write 1000 words a day, every day, you have your 30k book at the end of the month. If you can do 200 words a day, then that month still gets you to 6000 words. Thats a good chunk of your game and probably all of the core components to a point where you can test them.
Of course we cant always write every single day. So factor in 20% slippage and you won't be too disappointed but the point is to set a target and go for it. If your target is 300 words, then come hell or high water get on that keyboard and get 300 words on that page.
This is all ignoring all the other time that goes into creating a game (testing, evaluating, balancing, tweaking and revising) but none of those matter until you have words on a page.
There are a wealth of other options and resources for writing, many of which are applicable here but the above are some tips Ive used successfully.