The advice I was given by a professional physiotherapist was to concentrate on stride length, and landing on the backfoot (I pronate though, so this was probably foot shape specific). It may have beeny very generic advice and not something an Olympic champion would care about, but it helped my pace/lap time quite a lot.
Squats and glute exercises are worth considering too, especially if you are increasing your mileage fairly quickly, both help if you suffer from shin-splints.