What i learned from running X-country was, too many miles are bad, but
NOT AS BAD AS BAD FORM.
If nobody has ever taught you how to run, then find someone to teach you. If you are putting in 8 miles a day, and in bad form, you are going to get injuries, and those injuries are going to be permanent and lifelong.
If you run, do a rotation of types..
Monday) Intervals (if you can find a school track), Sprint 300 yards, walk the last 100 yards, and then sprint 300 walk 100 etc.. This teaches your muscles to build quick recovery. While your walking, fingers interlaced on the back of your head, open up the lungs and suck in as much air as possible. Don't stop moving through, and NEVER drink from a water fountain, you suck in a lot of air when you do, and get a mean side cramp from it.
Tuesday) Do some hills. Find a hill, go up. On top, do some leg workouts like grapevines, running lines on a tennis court, and jogging backwards (works the quads quite a bit and the calves)
Wednesday) LSD ~ Long Slow Distance. Go about 6-8miles but take it slow.
Thursday) No running! Recovery time. 1 cup sea salt in the bathtub, soak for 20 minutes. Get to bed early.
Friday) Sprints ~ 100 yard sprint, walk 300 yards, sprint 100 meters, walk 300 yards.
Saturday) Regular run. Get about 4 miles in the day time, and leave it at that.
Sunday) Day of rest so says God. So rest!
Before you do any running though, warm up. Slow jog, about 2 laps. Same with cooldown. Proper warmup and cooldown is essential.
The above workout is what I use to do in high school, so I know it works. If you want to, get some weights in on Tuesday and Friday. Remember, the resting days are just as important as the workout days.
So there you go, a running workout for the week. Intervals SUCK. Trust me, but those work your mental game as well as your conditioning.