I always check the dates on dairy products. Often there are multiple shipments of milk or yoghurt in the case and I try to choose a carton from the freshest batch.

I definitely check the dates on packaged meat. I once got sick from a package of ground beef marked "Manager's Special", i.e. being sold *on* its sell-by date.

Spices lose flavor pretty quickly. I usually buy them at an Indian grocer because they have more turnover (and lower prices) but it's definitely time for a purge.

I check the dates on things like chips, because they will begin to taste stale/rancid as the sell-by date approaches.

Canned goods? Nah. Though I do end up giving older stuff to an annual food drive so stuff doesn't linger that long.