I wouldn't optimize for the mom. Instead I'd look for anybody who didn't look like a fresh-faced teenager. Since I enjoy living near a grocery store that has reasonable prices, I also tend to recognize the workers. The ones who seem the most senior usually can work the till faster.
You're right about it not really being worth it for optimizing your waiting time. If there is only one checkout and it's some lady with 50 items and she's struggling with a checkbook, other cashiers will usually open up if you make eye contact with a free employee.
You'd save the most time by planning your shopping in advance. Make a list, and categorize it by food type. If you know your store layout, some time spent thinking about the order of you visit can pay off quite well. Plus, it helps reign in impulse purchases.
You're right about it not really being worth it for optimizing your waiting time. If there is only one checkout and it's some lady with 50 items and she's struggling with a checkbook, other cashiers will usually open up if you make eye contact with a free employee.
You'd save the most time by planning your shopping in advance. Make a list, and categorize it by food type. If you know your store layout, some time spent thinking about the order of you visit can pay off quite well. Plus, it helps reign in impulse purchases.