Light: place your cactus near a window that gets bright but indirect light. Do not place it directly in the hot sun.
Water: water your cactus when the soil dries out. Cacti are drought-tolerant plants and can be left without water for several weeks. Water once a month, or when a stick inserted to the bottom of the pot is still dry when pulled out.
Fertilize: once every six months use a water-soluble, slow-release fertilizer formulated for cacti