Drills are the only way I know of to improve your skills. You want to set up a few different drills that will help with your quickness, speed and ability to change direction quickly. One I use a lot is what I call, Quick feet
Set up some cones or markers about five yards apart and about five yards away and the last few close together. Then you can go thru the course as fast as they can without hitting the cones. When you get to the cones that are close together you will take smaller steps and faster. Another is run for five yards and then put one hand on the ground without letting your knees touch the turf then run as fast as you can for five more yards. (I will give the runner a ball to hold while he runs this drill).
Try to design your drills to help with speed and strength, I have used stairs or hills as well depends on what you have access to. Run up and down till your guys feel like they are going to come up thru your mouth
You also want to be able to change direction fast so run in a direction then stop quickly and go back the other way. I wish I could show you but there are a lot of books out there you could get. A couple would be football for Dummies and Youth Football Manual, they have a lot of drills you could use try the library first then Amazon.com
Watch film of good an bad runners, and try to figure out what makes some back successful, and others mediocre. You'll find out that that the great backs run then look, while the average backs look then run.
I agree with all of the above answers. I also want to say, to do these drills we must
make sure that we properly fuel are bodies . This means that we must eat the right foods at foods at the right times . Without the proper diet it is very easy to run into a trap. This trap that I'm talking about is what we call BURN-OUT . There are a few other reasons
for this burn-out but trying to do to much with to little in my opinon is the main
reason . Think of your body like a car . With little gas and oil in your car you
wouldn't get very far would you. Same for your body .