While shopping at Costco can feel like a total treasure hunt, you might just be making some major shopping mistakes along the way that put your membership at risk. If you’re looking to keep your grocery budget in order and discover only the best that Costco has to offer, you’ll want to keep reading for the most common mistakes to avoid when shopping there.Before you embark on your next trip, here are 7 mistakes you don’t want to make at Costco.1. Going in without a planCostco is huge, so goin...