I use a Kevlar tire. Mr. Tuffy tire liners. And a "thorn-proof" tube. Along with that I also hold the Mr. Tuffy in place with Duct Tape all the way around the inner part of the tire. Is this a bit of overkill? Possibly. But I have had fewer flats using this method.

And I absolutely stay AWAY from any sort of product such as "slime". I tried that and it managed to make quite the mess when I did get a puncture. Let alone messing up three pumps because that stuff came back through to valve stem.