There are daffodils suited to almost every garden situation: for lawns, borders, woods, rock gardens, cutting gardens, containers for patios and roofs, and for winter forcing. Catalogs that specialize in bulbs are full of information on which location each daffodil is suited for and how to plant and care for them.
In lawns or woodlands: Few things are as charming as a field of daffodils that looks as if it's growing wild. The key here is to make the flowers look wild when they're not. This is called "naturalizing" bulbs. The only thing natural about this is that the daffodils will increase in population each year, scattering themselves around. But it's the gardener's job to create a random-seeming initial planting.
The best way to do this is to toss handfuls of bulbs over the area you wish to cover. Plant them roughly as they fall, taking care that the bulbs are neither clumped together nor planted individually. Irregularly shaped, loosely planted clusters of 10 to 20 or more are best. You want space between the groupings so you can see the shape of the flowers against a simple backdrop of lawn or dirt. The flowers should look neither like a dense, yellow omelet on the lawn nor like distinct groupings. Blur the edges between groups and along the perimeter of the planted area so that the flowers do not cease abruptly but rather seem to have grown where they may.
You don't need your own meadow or forest to pull this off. Drifts of daffodils look great under spring-flowering trees, along the edges of shrubs or woodland, on a bank, or in an area of the lawn that you won't mind leaving uncut until the daffodil foliage dies back in summer.
In borders: Daffodils, like most bulbs, look dorky if planted in straight rows or individually. Here too they should be clumped together in little groups. Forget about bulb planters--they're for planting one bulb at a time--just dig a hole and put several bulbs in it. Have loose clusters of daffodils throughout the area you're working in, not just in one area of a border, so that there is a more complete and pleasing effect in the spring when not much else is in bloom. Also, by containing them in little groups, you can deal with the holes left behind by the bulbs after they've gone. You can also do this by planting, with them or very close by, something that blooms later--such as day lilies, hostas, or ferns--or by putting in a cluster of annuals each year.