In addition to writing for fun, I also write a lot for my day job. I regularly get stuck on what to say. Sometimes I start with my closing sentence because that's what I want to work towards. Other times, I walk away from the piece; I call it letting it marinate. I write it all down, whether it makes sense or not. Then let it marinate when I return in a week it starts to make sense and come together. And sometimes, I clean. Cleaning my house seems to provide writing inspiration.