For those of us who write and publish poetry this is a serious question. I came looking for 'what do people usually do' because I'm trying to set up a poetry book manuscript in Scrivener. 'Ask your publisher' is a good answer if you have one lined up!
I agree with Fortiter that it makes more sense to make each stanza a paragraph and use paragraph spacing to separate them. I used to do it that way -- but I found that sometimes my stanza breaks got lost in translation, especially on web magazines, so I have gone back to making each line a paragraph and indicating stanza breaks by blank lines, because that, clumsy as it is, makes it absolutely clear what's going on. It's worth remembering that much poetry publishing is done by amateurs with limited typesetting skills.
Another difficulty is that if there are really long lines that create a turnover (ie, wrap onto the following line -- think Walt Whitman!) you will probably want hanging indents for just those lines. The easiest way to to do that is to make the line a paragraph so you can manipulate the left indent and first-line indent.