You might want to use this as a guide on which to base your own workouts. Ran fast to the target, and then slow down back to your normal speed. Do this as you feel - pick targets close by and really sprint to them, or pick targets that are further away and run as fast as you can over the distance. Most good club runners try to do some strength work - for example, by running hills from time to time. As part of your build up to the marathon, you should spend a few weeks concentrating on strengthening your legs.
Recovery runs The key to training is recovery.
The stress you put on your body does not, of itself, make you fitter or a better runner. It is when your body recovers, and rebuilds the muscles, bones and other tissues, that you improve. This is why it is important to include rest as part of your programme. To help your body to recover, however, it helps to clear the lactic acid out of the muscles, and increase the blood flow. A recovery run should be a moderate pace and feel easy, and not much more than 20-30 minutes.