Too often people focus on changing foot strike, arm swing or a number of other 'easily' modified running mechanics. The question that should precede these changes is, 'does my body have the capability of making that change?'.
If you told most people to drop into the splits they would scoff, saying something like 'I've never been able to do the splits'. Why do we think it is any different in running? If you have never landed in a 'neutral' foot position, or without a gene valgus load why should you be able to change it on tomorrow morning's run.
Mold your body into the running machine you desire to get top performance from. This takes time, just like training for a race. Mechanics of running depend on multiple variables, so find someone to give you some insight on what variables you should be focusing on then get to work!