a good idea for a game jam is to have a concept written down and then plan spisific ideas at the end of each day so you have a durection and goals for then next one
Viewing post in How do you have fun during development?
once you have your ideas or if you are working in a team it might be useful putting them into an app like https://app.asana.com which allows you to add subtasks to your ideas without causing too much clutter and you have the option to only see things that are yet to be completed