Approach the purchase of Xeriscape plants as you would the purchase of any plant materials for your garden. Select healthy, robust plants to get a solid start. Check each plant for bruises or injuries before buying.
Some plants may be available from mail order catalogs. These plants may do fine, but be aware that the shipping method and shipping time can impact success rate.
Bring your landscape plan with you to the nursery or plant store. Discuss your ideas with the local experts and select Xeric plants that will work in your yard given the constraints of sun, shade, wind, water, etc.