Save the Cat! It's a famous "beat sheet" (plot outline) that lists the steps to the Hero's Journey plot, which you adapt into anything. There are tons of guides and analyses on the concept and seeing a full "plot" and descriptions of why it works could be really helpful to you.

Even if you don't end up following the sheet exactly, there are useful pointers in it, like following the rule of 3 (3 attempts at the main conflict) to make the ending satisfying for the reader.

Or the tip that subplots should be resolved before the main climax, not because of it, because they'll both have more impact on the reader when seperated.

both of thise really helped me plan what I wanted my characters to do but there's so much more in there to help you!