Here is a list of good and bad signs to look for during bunny bonding sessions:
Ignoring each other (this is good because they are choosing not to squabble or fight)
Lying next to each other
Mounting (they are establishing who is top bunny and this is important)*
Grooming (this is great!)
Bunny flop (this is AWESOME!)
Sharing the litter box
* Note: if the rabbit is mounting the other bunny's head, break it up, or the mounting bunny may end up with serious injuries if biting occurs.
Bad signs: (if you see some bad signs, don't worry, nearly all bonding rabbits have a few rough starts, just be patient, and make sure all the rabbits involved are spayed/neutered)
All these things are normal, it will just take some more time for them to get used to each other. The main thing is that you want to try to discourage these behaviors, break up any fights, and try to end the sessions on a good note.