As a teacher I try to never give a rule or a shortcut without explaining it or prompting the learner to discover why it works. The best way is to provide an activity that will illuminate the pattern so they can discover it and articulate it on their own.
A few of the learners I'm working with are close to discovering how to easily multiply by 10, 100 and higher powers of 10. I'm starting by having them color a hundred chart with the multiples of 10, and following up with this worksheet.
Then I'll let them practice with a Multiplying by Multiples of 10 worksheet from http://themathworksheetsite.com/.