Answer: In your area where the winter is relatively mild, soil preparation can often be done almost year round, and early spring greens can be planted in late winter so your time frame is more relaxed than it might be in a colder climate where the gardening months are more limited.
In all gardening, soil preparation is the most important step to success. You will want to run some soil tests and then make specific improvements based on the results and in view of what it is you wish to grow.
Generally, however, garden soil can almost always be improved by the addition of copious amounts of organic matter such as compost, rotted leaves, or aged stable manure and bedding. These materials can be worked in during the fall, or in the spring. They may also be used during the growing season as a natural mulch and will eventually break down to feed the soil. Since soil improvement is an ongoing process, it is never too early (or too late) to get started.
You might want to look at some basic gardening books to get an idea of how a "typical" gardening year would go. The "Dummies" series includes a number of excellent gardening titles covering a number of topics from basic Gardening to Vegetables and Perennials.
Good luck with your project!
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