What to Write about when you don't know what to Write about.
Not knowing what to write about is a wonderful place to write from.
Writing out of inspiration is wonderful—but it's also a bit of a crutch.
It's wonderful to just practice writing. No aim, no big idea, just the act of the craft of writing. Go sit by a stream and just write what you see. Go sit at a café and write what you see, as you'd sketch what you'd see. Write what you're going through. Write what you observe. Write what you're worked up about. Write what you're talking to your friends about already. Write what you know.
That's a powerful thing—and that connects writing with dharma, with meditation. Notice all the things you're inspired about or going through and write about them.
Write about little things, about details, and let that become your craft.
Try writing about what you notice—all five senses—in the comments below. Be specific, not theoretical. Don't think about what you want to say—focus on just describing what you see, hear, feel, taste, touch.