Ideas? How do they work for you?

So since I have been finished with draft 1.5 of my newest book, I've been busy critiquing others in my group. I haven't had time to write as of late with sick kids and some other chaos that has invaded my home as of late. This doesn't mean that I'm not thinking about my next project or even some revisions on my current one, because that's not the case. As a matter of fact, I have a name for the protagonist of my newest idea. Her name is Robin. That's it. I have a sort of formed idea, but nothing concrete enough to write down, but this is how it usually starts. I get a character then it goes from there.

For example, my current book that I'm searching an agent for started with an idea, around siblings. They were going to have powers. Then it went to powers controlled by the mind and it took off from there. I may be a plot person, who loves a good action scene and lots of cool things happening, but they still start with one thing and that is it still centers around characters.

How do you guys work through your ideas? Do you just write it all out and let it come out of the writing? Do you come up with characters first, or plot first and then come up with the characters? I'm just curious on how your ideas manifest.