Thanks for the responses above.
Okay, I’m answering my own question for posterity. This is for OS X 10.4 and the LG Dare with a formatted micro sd. (Format the card using the Dare Tools and Settings menu.)
1. Plug the phone into the computer via USB.
2. On the phone, go to Settings and Tools, select Tools and then USB Mass Storage.
3. The phone will show up as a mounted drive in the Finder. (Default is “NO NAME.” Change rename to a single word name, e.g. “Dare.”)
4. Drag and drop .m4a (or .mp3) music files via the Finder not iTunes into the “my_music” folder on the USB card. Also, don’t drag album folders, just the music tracks. DRM protected files .m4p won’t play.
5. Open TextEdit.
6. Paste the following Terminal command into TextEdit: “find /Volumes/Volumenamehere -name ”._*” -print0 | xargs -0 rm” (no quotes).
7. Change “Volumenamehere” to the name of the USB card.
8. Copy the edited Terminal command.
9. Open Terminal.
10. Paste and run command. This will delete the duplicate ”._*” files that OS X keeps hidden but that show up as duplicate tracks on the Dare.
11. .Eject the phone from the Finder.
12. Press “Exit” on the phone to Exit USB mass storage mode.
12a. (Power phone off and on again—seems to help with lock ups).
13. Open music player and wait for phone to initialize new tunes.
Note: The terminal command didn’t seem to catch all of those hidden files, so I’ll look that up again and see if there’s another version of that command that works better.