Include food plants too. Avoid spraying chemicals. If some control is necessary for beetles, sucking insects, or an overpopulation of caterpillars, use insecticidal soap, and apply late in the day when butterfly activity has ended. Hand removal is also an effective way to remove unwanted caterpillars. Include a water feature.
Butterflies drink from puddles on the ground.
A concrete birdbath top recessed in the ground can serve this purpose. These lists are not comprehensive by any means, but should give a good start to a successful and satisfying garden for butterflies.