Start a Ragnarok design diary and keep it with you, the diary can be digital or analog, so long as you have one, I use a list program and keep an individual list for each topic or idea, I add links or thoughts to those as they come up.
For board games, think of something like Ragnarok or MU online. For video games, absolutely any car racing game will fit the bill. You start at point A and you get to point B. The first player there wins. You can color it any way you like but that's the basic pattern of a race to the end game. So for step one, draw a line on a long sheet of paper.
You can make it straight or squiggly if you like. And when you're done, you're now over a quarter of the way finished. Next, draw a circle on both ends of the line. In one, write start and in the other, write finish.
Next divide up the line into spaces in which you can fit a coin. Hopefully, your line can hold at least 20 spaces. If not, that's okay, it'll just be a quick race. When you're done, your board should look like this. Step two in our exercise is to find a narrative.