Good advice so far, I'd add something that has worked for me: at the end of your riding each day, check your tires to see if they picked up any glass, wire, metal, etc. I think quite often my flats happened a ride or two after I picked up the debris. By finding it early and removing it, my rate of flatting has gone down dramatically. The only flats I've gotten in the past 5 years have been those damn radial wire shards which get through every tire I've tried. But, several times my inspection has found shards before they got all the way through to the tube.
I start at the valve and walk the bike while wiping the tire with a rage. If I find anything. I let the air out and remove the glass/metal/whatever with tweezers or needle nose pliers. If a big chunk of tire has been slashed, I'll fill the hole with ShoeGoo, reinflate and put the bike away for the next ride.