I check my tyres before every ride- unless I have only done a few miles on them since the last check. Normally I just find a bit of grit but after a long ride in the country- I found 4 thorns- 2 bits of glass and several bits of grit embedded in the rubber. Prise them out with a small screwdriver and they won't be in the tyre at the start of a ride to force their way through the rubber and into the tube. Mind you- two of those thorns had caused a puncture when I pulled them out- but it is easier to repair at home than on the road.

And I weigh 70kgs ride on Michelin PR2's in 700x23 and rarely get punctures. Puncture resistant tyres are around but I have not yet found the need for them. But Michelin PR2'sand Continental 4000s do have some puncture resistance built into them.