I took me some time to get my label printer from Brother up and running under Debian. In particular, it seemed like the printer is installed and known to the system, but it didn't print.
1. Download Linux drivers from the Brother home page (links bellow)
2. Install the drivers by running following commands:
$ sudo mkdir /var/spool/lpd $ sudo dpkg -i --force-all ql550lpr-1.0.1-0.i386.deb $ sudo dpkg -i --force-all ql550cupswrapper-1.0.1-0.i386.deb
Creating the /var/spool/lpd directory was crucial for me to get the printer up and running. Before I've done that the printer didn't want to print - even when the printer queue was saying that the document was printed.
Point your browser to http://localhost:631/ if you need the CUPS management console.
Brother offers templates for LibreOffice, so don't forget to download their "P-touch Vorlagen für Linux Office Applikationen" from the support page as well.