Weight training for running is quite basic. Focus on the following:
- dead lifts
- squats
- leg press
- calf raises (seated and/or standing)
- hamstring curls
You must go heavy, so that you can only do 6 to 8 reps per set. 3 sets each.
I put in one gym session a week, more or less doing the above.
The rest of the week I just try to do body weight type exercises and core (though I have been skimping on these the last couple of months!):
- planks
- side plank
- superman
- single leg squats
- single leg calve raises (on a step/ledge)
- hip bridges and thrusts
- lunges
- push ups
- mountain climbers