Of course! So as a general rule I avoid songs I know super well, because it's very easy to just gloss over them and not really listen because you know them so well, and I want you listen and hear the words and everything. That being said, if the song's perfect, it's perfect.

So I take songs I know vaguely that seem like they have SOMETHING--a line, a title, a topic, SOMETHING that makes you think it fits your book. Then I take songs I don't know--you know those albums you buy and never listen to, or the song a friend told you to get but you haven't listened yet, or that song that just showed up on your iTunes and you have no idea how? If the title sounds remotely related, do it. Get a whole bunch of songs.

Then just listen to them. Don't try to make an order. If a song turns out to have nothing to do with your book, axe it unceremoniously. An order will start to come out naturally. One of the songs will be something like an introduction to your MC, one will sound like the end, one will have a climax feel, whatever. Don't worry about being perfect. Shift the songs around. See what feels naturally after each other (on the playlist of my WIP, I have "Bleed Like Me"--which has a line "JT gets all fucked up in a karaoke bar/after two drinks he's a loser after three drinks he's a star/getting all nostalgic as he sings I Will Survive," and right after that I have the [incredible] Cake cover of "I Will Survive;" at another point I have a song that vaguely mentions an eating disorder but is mostly something else going into a song that is very clearly about an eating disorder--so that's the transition into the part dealing with the eating disorder, obviously.) Seriously, do not worry about getting it right. You can always move stuff around and add things you hear on TV later or whatever the hell you want.

The way it works well as a playlist is that you can look at it and be like "wow, this is a lot of slow songs right in a row. Something needs to HAPPEN" and you can see your book on this really macro level. Also it helps me remember what's happening next, because generally the 20 or so songs refer roughly to 20 or so scenes.

Hope that helps!