I am a certified (National Academy of Sports Medicine) personal trainer...and so hereby saying, DON'T STRETCH COLD MUSCLES!!! Warm up a bit (walk or slow run), move about, THEN stretch.
I am a hideous runner. I do run, and am sort of half thinking of trying to do a half marathon, just to see if I can. But I am awful. I put my ipod on and try to think of better things. The first mile is usually terrible, then I get into my stride (awkward as it is) and then I find myself having to slow down so I don't burn out. Blech.
Right now I am in MTB mode. I will stay in it until the weather gets too bad to do it consistently. I will run over the winter, then start on the road bike again in the spring.