Use visual cues when at all possible. Children with Aspergers are usually visual learners and they depend on these cues in their Aspergers education. They have difficulty processing oral language so hands-on, visual cues are a tremendous help.
Do not ask them to show their work on math problems. Children with Aspergers have the ability to come up with answers by processing the information in their heads. They may not even understand why you want them to show their work. A better solution is to ask them to explain the process to you. Do not waste time trying to get them to do something that will result in an unnecessary argument and nothing more.