I just kind of eyeball the bread. If it's just going a little stale, it becomes toast, but obviously if I see mold, into the trash it goes. Milk we go through pretty quickly, so I've only tossed the last splashes when the sell by date passes. But I usually do a bit of a sniff test when it gets around the date.
Everything else I kind of eyeball. I think because the stuff here is less well..full of chemical crap.
Soy products tend to last a lot longer, if you're looking to get more bang for your buck. But not everyone digs soy!