This really isn't a difficult thing to do, but since I needed to go sniffing around for clues to figure it out, I thought posting a tutorial would be a good idea.
- Do NOT let your DS lose power! No unplugging the battery!
- Have a Slot 1 flashcard
- Charge your battery
- Run NoFlashMe (downloadable here)
- Ignore anything that says "your DS isn't patched" or "short this pin" and press Start