I get a lot of flats. By good fortune they usually occur somewhere convenient; I can't count the number of times I have patched a tube sitting on the grass or a rock outcropping or a park bench in Central Park. Once my tire went flat just before I got on the subway (with my folding bike) so I fixed it on the train.

I always carry a patch kit, pump, and associated tools. I got a new patch kit a few weeks ago, and already used it up! Bad couple of weeks there.

I almost always carry a spare tube as well... just in case I screw up the valve again.

My bike has Schraeder valves, so I usually use Schwalbe tubes, because they have the threaded valve stem that is less susceptible to pump-inflicted damage.

Recently I also added a home-made "tire saver," a spoke mounted behind the BB and bent so it grazes along the surface of the tire and (in theory) dislodges any debris that has stuck to the tire. No flats since I added it!*

*anecdotal information only; obviously has no statistical or predictive value.