Hello XXXXXXXXXX
When the nails are dark colored and you can't see the stop you want to cut them a little bit at a time. After each cut you want to check the nail. If you see a pinkish or gray oval start to appear you want to stop. This means you are getting close to the stop.
If you have never trimmed the nails yourself you may want to take it to a vet or a groomer so you can observe how they do it. It is usually fairly cheap for a nail trim, usually between $10 and $20.
I am attaching some sites that will show you photos of exactly what to look for while trimming:
http://www.vetmed.wsu.edu/ClientED/dog_nails.aspx
http://www.ehow.com/how_2111213_cut-doggys-nails-home.html?ref=fuel&utm_source=yahoo&utm_medium=ssp&utm_campaign=yssp_art
I hope this information has helped.
Sincerely,
Bunny
If you have any further questions please let me know. Thank you.
Veterinary Assistant
10+ years at a veterinary clinic as a veterinary assistant. 20+ years raising/showing rabbits