I am conflicted about which one is appropriate for a story, or whether it makes a difference at all. A few years ago, god knows where, I've seen speech that was formatted like so:
—Hello. - Tom said.
and a more common form which is found in a lot of books:
"Hello," Tom said.
Does it make a difference, whatever one I use?
EDIT: I don't know how this displays since I am using my phone, but the first speech format was supposed to have a dash at the front in case it is replaced on your screen with a dot.