I'd second the Kanadia - I wore these at a very muddy race this weekend and was slipping a lot less than many of the people around me, there were really a lot of people sliding or falling over. I don't think I'm particularly nimble so it was either the shoes or a fluke!
That's my top tip, and is especially true when you want to increase the distance you're running. Try to get out at least 3 times a week. Build up the distance of one of your runs gradually, take walk breaks if you need to.