Youme I'll put together some pictures that may help. Yes there are things I look for but it is easier for me to show you than to try to explain in words only.
I have debated about doing a tutorial about this but most people seem to like the stack and whack which is ok because it is easy but I like to pick out my own designs. Stack and whack is somewhat accidental. You get whatever you get.
So I will post some pictures here soon.