Right, I don't remember the metal wires in the past. I picked up a couple recently, and only found them by knowing where the flat was in the tire.

Periodically I'll use the leather punch from a Swiss Army Knife to probe the bottom of every hole in the tire for glass and debris. Squeezing a deflated tire may help.

I'm now using puncture resistant tires, and doing much better at avoiding flats than I ever remember, and think they're even picking up less glass.

However, I've heard that winter and wet tires is worse than summer dry tires... I hadn't thought about it earlier, but so far, that seems to be the case this year.