When I flat on the road I pull out the old tube, pump it full of air with the mini pump, and find the hole. I then line the tube up with the tire to find where on my tire I flatted through. Then I thorougly inspect to see if there is any remaining debris. Then I run my fingers around the inside of the tire and rim just for good measure. I've yet to flat twice in quick succession. I tend to be lucky with flats though I think some of that luck is down to my equipment (I pick heavy, puncture resistant tires over light ones), and pumping up my tires before every ride.