Hi! I'm completely new to dressmaking and I've been following along with the book Love at First Stitch by Tilly. Some things are a bit vague so I've got a few questions about a skirt I'm working on.

1. I've seen conflicting info on how to finish seams (without a serger). The book instructs to straight stitch, trim the seam allowances, and then zig-zag stitch. But I've seen other people say to straight stitch zig-zag first and then trim the seam allowances. Personally this makes more sense to me, but I also don't know if it's the "right" way.
2. There are instructions in the book to press seams open or to the back of the skirt. I'm assuming there are pros and cons to each, but which to use in what situation?

I tried to look up this beforehand, but I could only find info on quilting and not dressmaking.