Not every child is likely to be a victim of bullying behavior. But those who are more prone to be picked on normally have these characteristics; low self esteem, insecure, lack of social skills, don't pick up on social cues, cry easily, emotional and unable to defend themselves.
If your child is being bullied at school or in the neighborhood discuss with them alternative ways of responding to the bullies. Tell them not to react, to walk away and get help if pursued, to sometimes agree with the bully and say "you're right" and leave, be assertive. We need to teach children to solve these kinds of problems and how to deal with them properly.