How do I transfer music on my desktop to my backflip?

If you dump them anywhere on the card, the phone will scan the card and know where they are.  They will be added to your options when you try to play music (by artist / album, etc.)

I don't know of a way to exclude a folder from being played yet.  I like to "shuffle all" but if I have mp3 ringertones, I obviously don't want them coming up in my mix.  I haven't figured (or looked into) out how to create playlists yet.

I dunno.  I used an app called Zedge, and the files are downloaded to my device.

You have to first, connect your phone to the computer.
When it's connected, itll ask you to bring up a folder, (which is your phone folder)
once that is done, go into what ever document folder your music is in & drag the songs you want into the phone folder. That is how I did it!