I've got a question on writing for games. Is there any paticular way a story for a game should be made or do you just write down the main plot and go from there?

There is no particular way, really, it's what you feel most comfortable doing. For example, on one of my current projects, I started with a very basic premise, fleshed it out a bit, and then began doing world-building, adjusting things I had already written to fit the new world.

One thing to keep in mind is that it also depends on your purpose. If you have a specific story you want to tell, then world building might come later in the process. However, if you're more interested in creating a world that you can tell multiple stories in, then world building should probably have top priority.

Yes, we've had threads once or twice where several people described what order they liked to do things in, and it was different for everyone. It also depends on the type of gameplay you are intending, for single-player games the main plot and characters are very important, while for multiplayer games the worldbuilding is usually most important.