This section is from the book "Culinary Herbs", by M. G. Kains. Also available from Amazon: Culinary Herbs, Their Cultivation, Harvesting, Curing and Uses.
In general, the most favorable exposure for an herb garden is toward the south, but lacking such an exposure should not deter one from planting herbs on a northern slope if this be the only site available. Indeed, such sites often prove remarkably good if other conditions are propitious and proper attention is given the plants. Similarly, a smooth, gently sloping surface is especially desirable, but even in gardens in which the ground is almost billowy the gardener may often take advantage of the irregularities by planting the moisture-loving plants in the hollows and those that like dry situations upon the ridges. Nothing like turning disadvantages to account!
No matter what the nature of the surface and the exposure, it is always advisable to give the herbs the most sunny spots in the garden, places where shade from trees, barns, other buildings and from fences cannot reach them. This is suggested because the development of the oils, upon which the flavoring of most of the herbs mainly depends, is best in full sunshine and the plants have more substance than when grown in the shade.
Combination Hand Plow, Harrow, Cultivator and Seed Drill