It's important to help children be selective about who they trust. But children are actually more likely to make fewer mistakes in their judgements of others if they have a basic motivation to trust rather than mistrust. Teach your children to see the good things in the world, and then when you work with them, you can use the method that allows you as a parent to do the best thing for your children the first time—instead of adding to the problems when you don't use the correct tools.