How do I teach my child how to keep safe from abuse?

Regularly talk with them about what how to react to a situation they are not comfortable with. Explain them what is and what isn't abuse (appropriately to their age), but also ask them what do they think about it. Ask them what situations make them uncomfortable or scared. Make sure they feel comfortable with sharing their good and bad expearienceses with you. Inform them about how and where to seek for help when you are not around.

I think you could try establishing a more personal connection with your child and be his/her best friend. Maybe then you could have a more open communication with him/her. The child would then discuss everything with you and you could guide him better about the people in his/her life, where he/she goes, how does he/she interact... hopefully, the more your child is under your guidance, the safer he/she is

By being honest and direct about the dangers out there and hope that when the time comes they will exercise good judgement.