Put a wash of watercolour on your page if you're using heavy stock in your journal—just having colour down helps get your creative juices flowing and will often lead you to the next step.
Make lists: there are a million lists we can make but I usually stick with 10—very doable, fast, and oddly satisfying. Favourite novels, pet names, cities, goals to accomplish, dreams, childhood memories... the list goes on.
Paste something, anything down. Even if you leave it for weeks, you've got it down now. I've learned that small bits turn into large volumes over time if you keep coming back. That's the joy in journaling—how it all comes together perfectly even without the "rule book." We're all just making it up as we go.