Head & Shoulders has unveiled The Good Girlfriend Guide, an e-manual of positive girlfriend-to-girlfriend advice tackling everything from beauty faux pas to relationship hang-ups—and consumers can access it from only one place: Barnes & Nobel’s Nook Store. The initiative started back in July when Head & Shoulders’ girlfriend ambassador, Alyson Hannigan, joined the brand to end “head-scratching’” behavior by encouraging women across the country to visit the Head * Should...