Ticks find someone or something to feed on through a process called questing. Ticks lay in leaf litter, crawl up the stems of grass or perch on the edge of a plant with their front legs extended. Here they wait until they are stimulated by certain chemicals like CO2 that are exhaled from their prey. They also respond to the heat and movement of the passerby.
Some animals, like deer and humans, apparently, release pheromones that attract the tick. When a warm, exhaling, potential host brushes by, the tick grabs on and settles onto the host. The tick snags the host’s fur, hair, clothing, or skin with its barbed front legs.