The best journal writing prompts are topics that you care about deeply and have strong emotions about. Often these are personal topics such as memories or reflections about friends and experiences. Memories provide rich possibilities for journaling. When writing a memory, you can transform the memory into a story with detailed description, conflict, characters and plot. Personal reflection is another category of journal topics that is usually prompted by a question like "Who am I?" or "What do I wish for?"
Starting a journal from a random topic sparks creativity and new lines of thinking. If you generate your own "random" prompts instead of looking online, they will be more meaningful. Begin by making lists of one-word answers to topics such as "what I want most in the world" or "creepy things." Then choose three words, each from a different list, and combine them to make a phrase. Use that phrase as a journal prompt.
An issue is a good prompt if you have a strong opinion about it. Anything that is open to debate can be an issue, whether it's a political question or about who should wash the dishes tonight. Choose an issue you care about, and debate your side in your journal entry. To further stretch your creativity, debate the opposing side.
Fiction prompts exercise your storytelling skills. A fiction prompt sets up the premise for a story, including at least one character and a conflict. Take a familiar story, such as a fairy tale, and rewrite it by changing one element.