A tropical lily's roots grow vertically. Place the plant in the center of the pot. Pack soil firmly with fist, being sure to leave the crown exposed. Marginals or bog plants are planted in the same manner as common annuals and perennials. Be careful not to cover the crown.
Lotus require a little more attention when potting.
Lotus tubers grow horizontally. Follow the same instructions for preparing the pot, but use at least a four to five gallon container. With your hand, form a one to two-inch trench along one side of the pot and place the tuber in the trench. Be careful not to break the growing tip then cover the tuber with soil pressing firmly but gently, leaving the growing tip exposed. Cover the soil with about an inch of gravel then add water before you place the plant in the pond.