I've posted this before, but I'm using this strategy again this year with many of my students, and it's working very well. I use this strategy to encourage students to line up at my classroom door promptly when asked. They really seem to enjoy it!
http://www.positivelyautism.com/downloads/LineUpStrategy.pdf
View more of Positively Autism's resources here:
http://www.positivelyautism.com/free/