As mentioned before, there are a few basic types of runs included in most successful programs.
These are designed to improve your endurance and are the most important aspect of your training. You should start out at a very relaxed effort to warm up properly for 2 miles and gradually settle into a relaxed pace that allows you to carry on a conversation.
At this effort, your body will best be able to make the physiological adaptations to improve your endurance. Any faster and you will sacrifice building your endurance for building speed. Since research has shown that to run the marathon involves 98% endurance and 2% speed, building speed will do you very little when it comes to the Second half of the marathon. For long runs, it is important not to mix speed with endurance (Only level HI schedules will call for the last few miles of some of your long runs to be run at goal pace). Make it a priority to drink plenty of fluids the day before, the day of, and the day after long runs to reduce the amount of dehydration that will occur. Be sure to gently stretch after the run, but plan to stretch more assertively the next day to help flush out the tightness.
These are designed to complement the weekend long run in improving your endurance. They should be run at the same effort as long runs. If your target race is a hilly one, you may want to find hills for this run.
These are primarily designed to improve your ability to handle the hills as well as to increase overall leg strength to make the flat parts easier to handle. They are also considered speed work in disguise since hills can raise your heart rate to the level achieved during a fast workout. First timers should run them at the same effort as long and semi-long runs. The only difference is to make sure that the course is a hilly one. Be sure to catch your breath fully in between the hills.
These are designed to allow your body to recover from the above runs while adding to your base mileage. As such, they are as important as the long runs in helping your body properly adapt to the higher mileage. Since their purpose is to help you recover more completely, you should start out at an extremely relaxed effort and gradually settle into a very relaxed effort. Typically they are run 1 minute-per-mile more slowly than your long runs. At this effort, your body is on automatic pilot and can more effectively circulate out the toxins (the natural waste products of muscle cell contractions) from your legs. Any faster and you will actually accumulate more toxins in the body. Most runners don't run slowly enough on their recovery days and end up injured or overtrained sooner or later since their bodies are not given the chance to recover enough. It is also important to run on the softest and flattest surface you can find to lessen the pounding on your body. The outside lanes of a high school track or dirt or asphalt creek trails are good options. If this isn't feasible, simply walk up and down steep or long uphills and downhills during your recovery run. Afterwards, stretch assertively for at least 10-15 minutes to improve your flexibility and squeeze out any remaining tightness.
Please Note: Fast workouts such as Goal Pace Runs, Long Fast Runs, and Short Fast Runs will be covered in the Level III section.