The Blank Page Syndrome

I want to write something. I really enjoy writing this journal, but I also want to write something else. Something longer. Fiction? Maybe. Magazine-style nonfiction? I’m not sure. I don’t know where or how to begin. I’m pretty good at staring at a blank page, just not so good at starting to write.
I’m not looking to write something to get published. I’m just getting that same itch to write I had in elementary school. I don’t know how many times I sat through a lesson not paying any attention to the teacher, but furiously writing the next chapter in my latest novel. I loved the feeling of being lost in the pencil lead. Usually, I’d get a few chapters into the story, then lose steam or lose interest. That’s my problem – I’m horrible at long-term planning. What do most writers do? Build an outline first, then write the book? How do you have “foreshadowing” if you don’t know what your character will do next?
It’s so much fun to see images in your head and watch them take shape in your words. I’ll think of something soon enough. The only way to make this itch go away is to scratch it.