Many gardeners like to naturalize daffodils—that is, to plant them so they look as though they have come up on their own. The ideal location is a rough grassy area that doesn't have to be mowed until the daffodil foliage yellows completely, in preparation for summer dormancy. If the foliage is cut prematurely, the daffodils may not flower the following spring.
The bulbs should be set out in informal groupings called drifts, rather than straight lines. To avoid any hint of human purpose, some people go so far as to toss the bulbs over their shoulders and plant them where they fall.