The latest WriYe Blogging Challenge was to admit the weird things you do when you plot. Honestly, I don't think I do anything weird when I plot!
Generally when I have an idea I jot it down in my notepad (or in my phone if I don't have paper to hand), then transfer it to my computer to flesh it out. I think about characters, then the story, then the details of the settings, and jot notes down as I think of them, then I rearrange them into some sort of order and save it.
Next I open a copy of the file, change the font colour to something bright, and start expanding on the sections in a black font, deleting the coloured text as I use those ideas. By the time I've finished doing that I've usually got a pretty cohesive plot outline, and sometimes even a couple of short scenes drafted out if inspitation has struck!
Sometimes I'll use Star Trek Online's character creator to get an idea of what my characters will look like, and that can help me when I'm writing later, or if the character is supposed to have a particular quirk. I'm not sure if that counts as weird, but it's the oddest thing I can think of!