This is something (we think) we finally understand after nearly two years of raising rabbits. So we think others might appreciate learning about it as well.
First, your rabbit has to conform to the ARBA standards of perfection for its breed. It will be checked for health, weight, color, sex, etc. You must bring your ARBA membership card. If you forget it, like my sisters did, you can't register the rabbit. However, I had my card, so we registered their rabbits in my name. You must also bring the pedigree. All the information on the pedigree will be copied by the registrar. This takes a bit of time, probably 10-15 minutes.
Your rabbit does not need to be a grand champion to become registered. Any rabbit conforming to the standard of perfection for that breed can be registered. It doesn't have to have won any legs yet. It costs $6.00 per rabbit to become registered. After all the paperwork is done and you have paid the fee, then the registrar will tattoo your rabbit in the right ear to prove its registration.
After it is registered, then you can apply (and send more money!) for the grand champion certificate, assuming it has earned enough legs.