This is a good question, and as I'm not a runner I don't really know the answer; it might be worth starting a new post to get people's opinions?
However, as a rule of thumb, training is specific -- so the best way of training to run is to run.
Gaining leg strength from strength training may help give you some extra explosive power in a sprint, but it's not going to improve your running as much as, well, actually running.
How much running you should do by way of training obviously depends on what kind of running you might need to do (short sprints? carrying things?) and how close you are to the necessary standard already.
Re: Opinion, I haz them
However, as a rule of thumb, training is specific -- so the best way of training to run is to run.
Gaining leg strength from strength training may help give you some extra explosive power in a sprint, but it's not going to improve your running as much as, well, actually running.
How much running you should do by way of training obviously depends on what kind of running you might need to do (short sprints? carrying things?) and how close you are to the necessary standard already.