Give consideration to the daylilies' height. Plant low growing varieties along walkways and in the fronts of beds while placing the taller varieties toward the back. If the background is dark, use lighter colored daylilies while if the background is light, use darker daylilies. While all the plants of one variety of daylily will bloom around the same time of year, different varieties may have quite different bloom times. There may be 6 weeks or more difference between early and late varieties peak bloom.
Most registered daylilies have a known peak bloom.
By selecting varieties that all have the same peak bloom, you can have a spectacular display for a few weeks or by selecting from a wide variety of bloom times, you can extend your daylily blooms for a much longer time. These companion plants can be used both to accent the daylilies and to provide color during the times that daylilies are not blooming. Your local nursery can usually provide you with more information about companion plants. I find that I can't follow most of the above suggestions because I am a daylily collector. I'm not really landscaping with daylilies but I use my flower beds to house my collection.