Many runners I know, do it just to do it. They go out and run, each day or every other day, and sometimes if they feel good they will push hard during a run. They will show up at the summer series and other races, race hard and be happy when they pr. But if you start to talk to them about a season plan or a lay out for the running year they shy away from it as a child does a difficult school subject.
I am not trying to compare an adult seeking to enrich their lives through a community athletic event to a pouting child. Rather, I point out that just like the child is nervous about the subject because they don't get the concept so too do runners shy away from long term and grander thinking because they are unfamiliar with the theories.
Other runners I know try to repeat the same week or two week period over and over again because some point in the past these workouts precursed a great race. What both of these fail to do is look beyond a kind of acute 5 - 15 day period to the larger frame of fitness.
USATF breaks the season into a preparatory phase, a pre-competitive phase and a competition phase with smaller training cycle's within. They use some pretty fancy USATF vernacular which I wont try to use, but rather condensed and in a laymen way it goes as follows.
1)Running to get ready to train : just easy running and one long run a week with an emphasis on establishing a good routine and getting mileage up.
2)Early quality training : easy running, a long run a week, and 2 or 3 w/o's a week gearing you for the next training with some emphasis on mileage still and perhaps a low key race to replace a w/o
3)High quality training : easy running, a long run a week and 2 or 3 w/o's a week that prepare you for the races to come and the occasional higher quality race
4)Racing : easy running, shorter long runs and 2 or 3 w/o's a week that are of less volume (not necasarilly intensity) with a clear emphasis on racing
A well organized season takes advantage of what was done before to accomplish the races and goals ahead. W/o's (workouts) can be done on hills, trails, roads and the track. Besides w/o's there is numerous supplemental training that can often make or break a season's goals if for nothing else prevent injury.
With this all being said you should remember that you get stronger the 24-72 hours after races and w/o's because your body has overcompensated for the damage that was done. This is an acute example of loading (the w/o or race) and unloading (the rest and easy runs over the next 24-72 hours). So if the body is subjected to a larger scale stress, set w/o's for a 3 or 4 week period, you will reap the benefits the weeks following.
If you are interested in this please check www.usatf.com and look under the coaching education section for related work, Jack Daniel's Running Formula is another great source, and as always my ears are open.