Priming is a strategy that parents can use at home to help their children prepare for upcoming activities. As an antecedent intervention, priming is a research-supported intervention method for students with autism. The idea behind priming is to preview activities or information with a student before the student participates in that activity. Priming consists of three components: (1) it is conducted prior to an activitiy and should use the same materials, (2) priming should be a low-demand situation, focusing on tasks that are easy for the student, and (3) priming should incorporate frequent opportunities for reinforcement.
Since we know that many students with autism are more comfortable with routines and things that are familiar to them, one goal of priming is to help the student become more familiar and comfortable with activities that will be presented as school, an ABA clinic, a playgroup, or other settings.
Here's a guide to priming with helpful examples: http://www.txautism.net/docs/Guide/Interventions/Priming.pdf
"Priming as a Method of Coordinating Educational Services for Students with Autism" by L. K. Koegel, R. L. Koegel, W. Frea, and I. Green-Hopkins. Language, Speech, and Hearing Services in Schools, Volume 34 (2003).
"Including Children With Autism in General Education Classrooms: A Review of Effective Strategies" by J. K. Harrower and G. Dunlap. Behavior Modification, Volume 25, Issue 5 (2001).
"Teaching Preschool Age Autistic Children to Make Spontaneous Initiations to Peers Using Priming" by K. Zanolli, D. Daggett, and T. Adams. Journal of Autism and Developmental Disorders, Volume 26, Issue 4 (1996)