If it smells and looks fine, I'll eat/drink it. I'm currently using milk with a sell-by date of January 22nd in my coffee. It's right on the verge of expiring, but it will be good enough for tomorrow's coffee. Sell-by and use-by are different things. My brother has a similar policy, except he also has a policy of DO NOT LOOK AT EXPIRATION DATES ON CONDIMENTS. Jams, mustard (which actually shouldn't go bad, but that's a whole separate thing), real maple syrup (if it's refrigerated after opening, it never goes bad. If it's *not* refrigerated once it's open, I've been told it develops a toxin), ketchup, bbq sauce, pickles -- if it goes on a sandwich and is not meat or cheese, expiration dates are ignored. Honestly, in our family, we probably only use expiration dates as a "Well, the date on this is four years ago, so if I haven't eaten it by now, I doubt I'll ever eat it" guide to tossing it. We're *really* bad about cleaning the fridge.
After last weekend, though, I won't use baking mixes (cornbread, brownies, cake, etc.) after the expiration date. The leavening stuff stops working after a certain amount of time, so you will end up with cornbrick rather than cornbread. It was as dense as polenta.