Assuming you're talking about running faster, as far as legs go you'll actually want to be working your Glute, Quad, and Calf muscles.
This doesn't mean you should also neglect working complimentary muscles such as the Tibialis or the Hamstrings. Focusing on one side of any symmetrical muscle can lead to some pretty weird abnormalities, so I've been told (ie: only working abs, neglecting the back, only working biceps, neglecting triceps,) so don't get into any bad habits.
Also, before you start hitting the Good-mornings make SURE you have a very strong core (ie: back-extensions and abdominal work.) I'd recommend warming up your back before doing any Good-mornings.
As far as the number of reps and sets, it depends on what type of running you're doing. Since you said you want to run faster, I'd go with low-rep sets. Maybe starting at 3 sets of 5-8 repetitions once a week, adding one set every two weeks until you're doing 5 sets. Whatever you do, make absolutely SURE you're also incorporating leg-speed training into your week while you're power-lifting. Otherwise you will run around like a truck in low-gear.
Keep in mind there is nothing in this that will give you any sort of muscle endurance. This will pretty-much train your legs to have incredible bursts of speed for short periods of time. What I would do is first focus on high-rep sets, 4-5 sets of 15-20 reps, for a month or so and then begin bulking until you've reached a strength you're comfortable with. After that, go back to the endurance-lifting. This will generate more than speed, it'll give you power.
Hope this helps.