Pen and paper is how I do it. I keep track of what I planted the previous year and if it grew well where it was, which helps me draw up the plan for the next year.
A fair amount of experimentation goes into it though—I usually pick a new type of plant to grow each year. Some recent picks were multi-colored carrots, spaghetti squash, and cinnamon basil. But I'm not a hardcore gardener by any means.
I hope your garden turned out well this year!
I'm not very organised on paper but I love my pollinator plants and try to focus on resilience. I have kept every tag from plants I have planted even if they did not survive.
I store my seeds by the time of year that I sow them (vertically so I can sort through quickly enough).
Then I do a walk through with my phone video at different times of year. Between the videos and the photos I have a nice visual reference of what was looking happy in the garden at different times of year.
Lastly I have a insect ID app (Picture Insect) for pollinators and pests. My photos in there and the dates can tell me which plants were good hosts to pollinators, which were harmed etc.