Like its teeth a rabbit's nails grow remarkably quickly and will need trimming around once every two months although this does depend on how much your rabbit is able to wander around and dig in the garden. A simple guide is to make sure that your rabbit's nails don't stick out beyond the fur.
How to trim their nails
You need to trim the nails back to half a centimetre from the quick which is the pink fleshy part inside the nail. On most nails you can actually see this fleshy part of the nail, but is can be harder to see in darker nails. If the nail bleeds you can use a bit of cotton wool to apply a little pressure.
Going to the vet
If you are not happy holding your rabbit then a vet will be happy to trim its nails for a small fee.