And you might want to do a search for Dr. Geep's tutorial on lights and shadows--he has one series of pictures rendered at all sorts of different settings, so that you can look at the ways your settings influence the shadows that you are going to get. The subject can quickly get really complex, so pick one or two things to experiment with and try not to get too overwhelmed! There's been a huge improvement in my shadows just by selecting each shadowcam and zooming in (as mentioned above in message 3). Good luck :)