Why lift? To become a better runner.
How does this do this? By improving running economy.
How does lifting improve running economy? By improving the force production and power potential in the muscles used in running. You reduce the O2 cost of running at a certain speed. As long as body weight is maintained.
How do you lift for strength and power? Approx 85% 1RM, or sets of 4-6 reps. Periods of heavier single sets of 1-3 at 90-95% 1RM are also advised. Periods of lighter weights (30-50% 1RM) performed explosively (explosive/fast concentric phase) are also advised. Plyos are also advised. 2-3min rest between sets.
How often? 1-2 days a week on your harder running days to consolidate higher stress days.
How much? 30-45 minutes should be more than enough.
What exercises? Compound movements using a barbell that use your legs, with minimal technical instruction required. Front Squat and Trap Bar Deadlift meet this definition.
What about the upper body? Minimally required. Used to assist the more important lower body movements. Dips and Pullups are fine.
Alan