Start around age 2.5-3 by teaching about private parts and who can touch them for cleaning or medical checkups. Use yes-and-no type conversations. Teach them to always keep a trusted adult in their line of sight — practice this at parks and cafes. Gradually introduce the concept of building trust and recognising who to trust. Avoid fear-based language. By age 3, you can introduce good touch and bad touch concepts. Daily practice helps them retain these lessons even at a young age.