The best sign is when they start grooming....it means they have accepted each other and sorted out who is boss.
We put them both in a neutral run (or kitchen if it rains) with some food, 2 hidey holes and toys and sit with them armed with a water spray in case they fight.
Its normal for them to chase, mount and pull fur......if they nip or lunge or vocalise in a growl give them a spritz with the water......if they grab each other by the head and hang on, kick or cause injuries to each other then stop, its the clearest sign you can get that they are probably not meant for each other.
I tend to leave them together continually from day one so bond when you have free time to watch them, at least for the first 3 hours. After that if all is well they can be left but checked on every 30 minutes.
They can usually go into a (neutral) hutch by night fall and I watch them for 30 minutes after this as its normal for chasing, mounting etc to start again. If its too rough I put them in the kitchen for the night.
By 48 hours they are usually living in the same hutch and within 3 to 5 days mist coupoles have started grooming.
My longest bond took 3 weeks but I never seperated them once I started, if they fight and you break them up then put them back together the last thing they remember is that this horrid bunny attacked them....so they get in there first.
Hope this helps.