If you mean the one on Windows Phone, my biggest "tip" is to remember to save frequently. >_>b It doesn't seem to automatically sync and I lost part of a draft that way.
My second is that copying-and-pasting from a Word document on OneDrive (that you created on your phone) into plaintext brings with it some hidden formatting, especially related to paragraphs. Since I found that out I've started using OneNote to write drafts for my stories, although Word seems to work okay for articles since they aren't plaintext.