Back when I was plotting and planning the garden last winter, I made a spreadsheet (old habits die hard) to help me visualize how it all would work. This proved to be an invaluable tool for planning seed purchases, harvest cycles, working with the space and making my life easier once things started rolling. I just kept tweaking it as things evolved and now it stands as a record of this year's activity.
That's it. That's my garden journal. That's all I need to plan crop rotation, seed management and prepare harvest strategies. It's important to not bog yourself down in this process. DO keep track of what you planted. DO make notes about what worked and what didn't. Take LOTS of pictures! DON'T sweat the small stuff! If you are enjoying the process, then your garden is working! If you had a tough year due to pests or lack of rain, keep the faith. As the saying goes...there's always next year!