Soil conditions can vary from one location to another, so you will likely have to experiment to see what works best. But there are some general facts regarding soil preparation that are important to know.
Preparing Your Field
If you are preparing a field that has been in pasture or uncultivated for a number of years, you will have accumulated a large seed bank....that is a large number of weed seeds that have not germinated. Although a filed may look good after it is rototilled, the weeds will appear in large numbers once the conditions are right for germination.
The best approach is to prepare the field a year in advance. Rototill the field and let the weeds grow, and plow or rototill before the weeds go to seed. Doing this several times will significantly reduce the amount of weed growth that you will have.
The picture below shows a portion of a field that was heavy with weeds, and the number of weed seeds that germinated once the conditions were right. A month earlier this field looked like good plantable black dirt.
Garlic is a "hungry" grower and the bulb sizes produced can vary significantly based on the nutrient composition in your soil. We began with a well composted mushroom manure in our first year to compliment a field that had been in pasture for about 15 years. At the end of the rows, we ran short of manure and planted in the unfertilized soil as well as where we had spread the manure. The garlic plants that were well fertilzed had stalks up to three feet in height and produced large robust bulbs. Those at the end of the row where the fertilizer was thin grew only to a height of about 15 inches and many of the bulbs were less than an inch in diameter.
We use raised beds for a number of reasons. At the west coast we receive a lot of rain and a raised bed of about 8-10 inches provides good drainage during the wet seasons. We also minimize the width of the pathways to about 16 inches with beds approximately 40 inches. We found that wider pathways only provided another place for weeds to grow!
Planting normally occurs in late September or early October. Once the beds are prepared, the cloves must be separated from bulbs, and we normally do this one or two days before planting. The individual cloves are planted about 1-2 inches deep with the basil (root end) of the garlic pointed down and the pointed end of the garlic upwards.
With a little preparation and planning a couple of people can plant about 1000 garlic plants in a couple of hours once the cloves are sepaarted from the bulbs.