Heading to the supermarket with a shopping list is one thing, but leaving with what you need is another entirely. Yes, they stock charcoal; but should you buy briquettes or hardwood? Your buddy loves shrimp; do you get large or jumbo? For every summer essential, there seems to be a confusing variation — cilantro or parsley, whipping cream or heavy cream. Here, a cheat sheet to a half dozen shopping conundrums. Remember it the next time you hit the store and you'll come out a winner.