Kathy Mack has posted two fantastic backing tutorials on her Pink Chalk Studio blog. The first tutorial is for non-directional prints using a side-to-side method; the second method is a pieced method that is best for directional prints. Check 'em out!
Kathy is another fantastic teacher - be sure to subscribe to the Pink Chalk Studio blog and download her tutorials. She also has a great online fabric shop, Pink Chalk Fabrics - don't miss it: