What are effective ways to correct bad behavior in children with autism?

Redirection. As with most kids, trying to change what is happening at the moment by directing the child to do something different. We too often yell at kids for bad behavior, so pick your battles and save the important reprimands for major stuff. Most of the other behaviors should attempted to be changed by reinforcement of new projects or challenges.
Maladaptive, not bad. Children with autism act out to avoid non-preferred tasks, continue preferred tasks or attain desired objects. One technique to address maladaptive behaviors that keep a child with autism from learning is applied behavioral analysis. The child is immediately rewarded for following precise directions, while off-task or tantruming behaviors are ignored.
Autism. Autistic children with behavioral problems is a difficult issue to correct. When needed to correct a behavior you need to maintain eye contact with the child and repeat the issue over and over again in a quiet environment without many distractions.