Cross Training To get better at running you really need to run. Firstly there is little real benefit if you are well trained. Cycling can help by strengthening opposing leg muscles thereby avoiding injury. Cycling uphill has some cross over with hill running. Weight training can also strengthen opposing leg muscles, strengthen stomach muscles and the upper body although this may or may not affect performance.
Swimming can help with recovery from pavement pounding and hard sessions.
Diary Running diaries are a significant potential performance enhancer. Analysis of well filled in diaries can lead to understanding of how you improve, and also show how to avoid injury. They should include course details, environmental conditions and how you felt. It is also important to record resting pulse and your weight. There are now many software packages which can make the recording and analysis much less of a chore.