Where to Start?

An idea comes along, it could be a book, novella, short story or whatever. The kernel of inspiration is there but what next? Where do you start?

Here are a few options:
Character
Setting
World
Plot

There are a few other options too. The main set of two, to choose from first is whether to do prep work (world building, outlining, etc) or to just write. In general, I do the latter. I write and worry about the other stuff later in the rewrite, edits. However, I've done prep work before nanowrimo in the past and know a few who do full world building before even figuring out the character that will experience the story. Either way, the method of the idea, what sparks the desire to write that one, can be one of the four sections mentioned above.

What comes first to you?

For me, it is character or a scene of the plot. Those are the top two. But what is the difference?

Character
When character comes first, there is a person aka someone for the reader to become attached to and for the conflicts to occur. Without character the story would be hard to fall since it would just be about the events and the reader wouldn't see or feel what those events cause.  Some get their character first and the character can be one of the most important aspects of the story. Character driven is popular to say the least. However, sometimes when a random character comes to mind it can be difficult because without a plot then it's just reading about a person and their day to day routine, which is very boring. It's hard to write about a character and have no idea what to do with them in order to get a stroy.

Plot
The what if factor in the story. What happens? Some people do come up with these first and then figure the rest of the aspects out later. A close friend of mine does the world building, has the idea for the story and then finds characters to fit within the plot to make it work. I can't do this much. I need a character and then figure out the plot. It is good to have something happen, a conflict, but without a good character to experience the plot, it will also be difficult.

Like most of writing, what comes first is dependent on a number of things. Not everyone works the same. Some will spend years figuring out the world and then do the writing. Others will find the character and then write from their viewpoint to discover the plot. It's the type of situation in writing where the advice for success is to simply Do what works best for you.

What comes first for you?
Do you do prep work or begin writing at once?