I'm a fan of placeholders while I write. I use them for names, scenes, moments, and pretty much anything else I'm not tackling right that second. For instance, you can't write everything at once but sometimes ideas come in clumps. So instead of either jumping around and finishing nothing or feeling paralyzed because I don't know what to focus on, I take a minute to write a brief placeholder. That way I don't forget about my idea, but at the same time, I can keep moving forward with what I'm already writing.
It's basically in-line note taking. It's right in the manuscript so I can't lose it. And I won't forget to work on it later when I have time. I write my placeholders in all caps because I've found they're easier to see that way when I'm scrolling through my book. It's also a handy method when you haven't named a character yet but you don't want to stop to figure one out. I often just put "NAME" as I write.
Do you use a similar method when you write or something totally different?