I like line spacing of 1.2, which also happens to be the default in Kindle ebooks.
You might also pad a bit between paragraphs. You can see this in most Big Five books, at least on some pages where the book designer is evening out the display on the left- and right-hand pages.
I do this in OpenOffice Writer, whose menus are more intuitive and whose PDF output is more trustworthy than Word's. Between hyphenating, tracking, and adjusting line width, properly formatting and proofing a print edition takes a week or more. Never forget that you are competing against professionals who spending a year making a typical book ready for sale on publication day.