I like to square as I go. If the units that go into a block aren't right to start with, my block will never be either.
I also do a lot of paper piecing. I've got Eq6 on my computer and if I can paper piece the unit I do. A lot of paper piecing can be "chain pieced" if the units are complex. It goes faster and my blocks look better in the end.
You will find what works best for YOU...
Julie