Answer: You can plant in any arrangement that suits you, however it is good to plant so that taller plants will not shade their neighbors.
Another point to keep in mind is you should be following a routine of crop rotation so that you are not planting members of the same family in the same spot until several years have passed. This is especially important to help limit pest and disease problems recurring from year to year.
You might have an area that is naturally wetter or drier, or richer or leaner, and would try to plant something that prefers that type of soil condition in that location. Or you might group crops that require extra irrigation in one area together and water heavily only in that part of the garden.
Some gardeners try to follow a system of companion planting where they plant neighboring plants, including herbs, in a way that might be beneficial. There is a listing of such combinations at the following web page from the North Dakota extension. You might find it useful in planning, as well as the above principles.
You may need to cut and paste the complete url into your browser to make it work correctly.
I hope this answers your question.
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