At least, that’s the short version of the answer.
The slightly longer version of the answer would be: how long has the original author or speaker been dead?
This has come up a few times when I wanted to quote more than just the title of a song or poem. The rough rule of thumb for fair use in a commercial setting (your book) that I was given has been five words. If you quote more than five recognizable words, then you are getting into copyright law’s turf. The rule comes from academia, specifically what constitutes plagiarism, and a real copyright law site suggests that you can go a touch farther. In one case, I knew I didn’t have a prayer of using the lyric, because it was (and as far as I know, still is) tied up in a nasty copyright fight between a performer and the writer of the song, and the distributor. That’s the sort of fight no author wants to wade into, so I made up some lyrics that fit the mood of the song and went from there.
Making up something is always safe. Doing your own translations is also safe.
The rule of thumb for most printed works is: has the author or artist been dead for more than seventy (70) years? If so, the work is probably in public domain, and you may quote away. There are some exceptions for archival material and stories that were copyrighted by an institution or publication, but if you want to quote Arthur Conan Doyle or Rudyard Kipling, or Robert Browning, go for it.
If you are outside of the US, please, please check your nation’s laws. Some have shorter copyright spans, some longer. If you might get sued over it, do your homework first. Spare yourself the pain.
If you do choose to quote something under fair use, such as having your protagonist quote Raymond Chandler’s “A blond to make a bishop kick a hole in a stained-glass window,” (from Farewell My Lovely), include the source in your acknowledgements page, or works cited. Will this keep you safe? It is not a 100% guarantee, but the fact that you gave proper credit can mollify some authors or composers.
Sometimes. The fact that your work is for sale tips the balance toward a stricter standard for what requires payment of permissions fees as compared to what is free Fair Use.
Some fights are not worth picking. If you are not completely certain if you can cite or quote a song, poem, or book through fair use, think long and hard of you really need that. If so, you need to start digging for the copyright holder (not always clear) and then find out what the fees are. Especially if the lyrics are from a source that is well-known for protecting its brand.
Below are some starting sources, with general information. The US Copyright office also has a web site with good to decent information. The government doesn’t always keep up with what the courts rule, so some things might end up being a little different “in the wild.”
This article from nolo.com is a good introduction.
Now, something that I encountered for the first time recently: Do you post excerpts of a work on your website or blog? If so, especially if it is a short work, make sure to remove them before you upload your book to sell (unless you are truly indie.) Leaving a certain percentage on-line without a paywall can trigger the “Do you really own this?” query from e-book distributors, which delays your release. It’s not copyright per-se, but something you do need to be aware of.
Set eighteen months before Eerily Familiar, Lelia and Tay go west to study. They have survived the schlorp-monster, a mage gone bad, and Mr. Lee’s exceedingly strong cinnamon candy. But can they survive . . . the Grandmother.