I don't consider myself a shadowing goddess but when I have time, I like to tweak shadows and play around with customizing them. I use a mix of shadow styles I've acquired over the years, but I often tweak at the very least the opacity, and I set the angle to 45 degrees. The one thing that I'm kind of anal about is keeping it at least somewhat realistic. So I'm not going to put a tiny shadow on an object (even a photo) that's sitting on top of a big bulky item like a flower.
I also like to use the wave tool on my shadow layers on some layouts (again, if I have time) as described in
this tutorial by Jacinda. I usually hit the randomize button for each new layer and sometimes adjust the number of waves or the wavelength settings for each new layer that I'm using this process on, just so it looks more random and natural.