As they fight for survival in the era of online shopping, brick-and-mortar retailers are cutting costs by slashing head count and budgets for training. But that erodes their biggest edge over e-tailers: a live person customers can talk to face-to-face. For every dollar a retailer saves on staffing, it may be losing several dollars in revenues and gross profits if customers leave stores empty-handed because they can't find a knowledgeable salesperson to help them. The solution lies in optimizing staffing and training for each store, but most retailers don't know how to do that. This article offers them a step-by-step approach. It involves analyzing historical data, conducting experiments, and assessing the results, and when applied systematically can add as much as 20% to the revenues of existing stores. Even better, if staffing increases at some stores are offset by cuts at others, and vendors fund product training, those higher sales will cost retailers little or nothing to generate.