In my head, there's this scene where my two main characters are running through a dense, dark forest to escape drones and helicopters. I have a lot of stuff in my head for the scene, but I'm missing one thing: the opening. I want the whole thing to make the reader really feel the panic and paranoia the main characters feel as they run for their lives. How do I kick it off? Do they start out by relaxing and then noticing the drones, are they walking through the forest, or do I start off by them running? Do I start with dialogue? I sit with pen and paper for hours, I sit in front to the computer with my Word open for hours, and I can't bring myself to write even one single word because not knowing how to start throws me off so much.