Intensive organic garden planning on a yearly basis involves three basic concepts: successions, interplanting and crop rotation. Each spring you should draw up a garden plan that lays out the location of the crops you’ll grow for that season, both those that will occupy a spot for the whole season, and those that may just occupy a spot as a quick crop, a green manure, or part of a short crop succession. Each of these seasonal plans should be kept with your garden journal, so that year to year you can keep track of what has grown where, and balance the demands that each crop makes on the soil. Over time you’ll be able to use these records to develop a system of planting that will give the best possible results in your garden.
This is the most important book you can own, though, it will, by necessity, start out blank. A garden journal—that records the weather, your garden activities for the day, the names of plants and the conditions under which they were seeded, planted, cultivated, or harvested, and the results of those activities—will, over time, give you the kind of site-specific information that no other source can provide. Within a very few seasons you will know, with as much certainty as is possible, which plants do will in your garden, and when you should see or set them out for the best results. You will know how many plants you want or need to get a given yield, and which spots in your garden are warmer or colder, wetter or drier.
If books are too old school for you, keep a blog and post photos, planting records and observations on it. It will serve the same purpose, and if you want to share it with others, it will be that much easier. And in doing so you’ll be adding to the accumulated human knowledge of horticulture.