I have no idea if my shadows are "good" or "bad" but in the end all I care about is whether or not I like my page, including the shadows. To be honest I don't do shadows the same every time. I basically look at my page as if it were a paper page and try to make the shadows look "real." I also think shadowing to some extent is personal preference - for example, I really dislike "floating" elements or papers, they don't like realistic to me, but I see layouts like this all the time that are gorgeous layouts, but I just prefer my papers to be more realistic - a paper layout isn't going to have a paper mat with a deep shadow unless it's been pop dotted, kwim? In my clusters I just shadow to make it look "real" - bigger, bulkier flowers get heavier shadows, smaller more delicate flowers less, etc.