A ton of positive reinforcement!
When it comes to disciplining children with special needs you really can't go wrong with positive reinforcement. Many of these children lack an internal drive for behavior due to impulsiveness. It's not their fault, it's just who they are! You need to replace that with something, and having that desire for positive behavior come from a trusted adult is a great alternative while they grow the skills to have use internal drive for checking their own behavior.
Try to catch them doing the right things and call them out for it! They really want to make you happy, it's just hard for them sometimes.