The best way to grow them is to twist the top off instead of cutting off the top. Twisting will leave less fruit attached to the crown so less chances of rot. After twisting off the crown, peel off the bottom inch or so of leaves. It will leave an exposed area to plant. Let the crown dry out in the shade for a day and then plant it directly in soil. Rooting it in water is a waste of time.
One plant will give you one fruit usually. As a home gardener, you could probably plant them 1ft apart.