I haven't a clue at this moment how to tell you to do it, but I know there are tools out there. Appears LJ is going under...
The Russian Bear Slashes a Social NetworkCourtesy
snackpants Update:
Changes at LJ HQCourtesy
alice_bunnie Finding a good backup tool and using it might still be a good idea, if you're particularly partial to your journal and the loss of which might cause you some misery. Of course, saying you should keep backups is like saying "water is wet" or "air is nice to breathe", so you can officially file this journal post under D for "duh!"