Repairing a project

Are there videos available that show how to “tear” something out? Go back a few rows if you’ve made a mistake? I recently messed up a project and took my project in to a local yarn shop to get help, but I’d love to be able to do this myself so I didn’t have to bother others. (The wonderful person took my project back two rows–back to a “clean” row so I could start again.) Thank you.

Sure, scroll down to ‘fixing mistakes’ on this page.
http://www.knittinghelp.com/videos/knitting-tips