In the words of the staff at Fine Gardening, this is a plant that prefers neglect. Leave it alone and it will produce lovely green foliage and delicate white flowers with a delicious smell. Pretty good deal, if you ask me!
Keep in mind that "drought tolerant" doesn't mean "can be ignored." These plants should all be provided with ample fertilizer and mulch to support them, and they will need to be watered. Offer them occasional deep waterings to encourage them to root deeply in the soil and seek out their own sources of water, and as they get established, you can taper back on the watering. Be aware that extreme drought and heat can kill even the hardiest of plants!