Runner's World has lots of good information on their site about training. The thing to keep in mind is that to increase distance and speed takes two different types of training. For distance, do a slow/easy run - or run/walk, and gradually increase your distance each week. This will build your endurance. For more speed, do interval training (easy run, run at a moderate tempo, easy run) over a shorter distance. As most any running site will tell you, if you train at 80-85% of your MHR all the time, you won't see much improvement - even though you are getting exercise.

Personally, I love running and conquering distance barriers. It's not all about speed. But if you prefer walking or cycling, that's good, too - they're both great exercise. Run the 5K or walk it - lots of people walk in 5K's. It always feels good to finish, especially if it's a charity event.

Deb