I think a lot of us bunny owners have been there, wondering if our buns weren't lonely when we're not there. But then there are precautions you must take if you want to be sure you will effectively give your bun a friend instead of a
hated rival.
First of all, your bunny and their new friend
should both have been spayed/neutered for at least 2 months before you even try to bond them.
The reasons are multiple: Basically, spaying/neutering not only eliminates risks of cancer especially for females, by numbing their reproductive instincts, it generally makes bunnies calmer and if your first bunny was litter trained, there are less chances that they will forget their toilet manners once introduced to an
invader (You don't want to experience
'Poop wars' , where each tries to spread their scent everywhere and of course outside of the litter box, so ALL the area becomes toilet). You will have way less possibilities of (possibly lethal) fights for dominance or territory too. Because believe me, when a bunny or worse,
two, have decided they hate each others, they will try to kill even through bars. But even if they are not fighting, I'm sure you still will want to avoid them spraying pee everywhere on things they want to claim, including the other bunny they want to show who Boss is, and also chasing and humping, nipping and biting both the other rabbit, but possibly also
you because your place in the house will change too
. I have had that problem in the past, with my very adorable and cuddly little female becoming
untouchable (grunting, nipping, hitting with both front paws each time I tried to touch her) after I introduced her a rescue male, and even after I got him neutered, it took me months before,
I ,managed to rebond with her. She also got food aggressive, which means that she would start by attacking the other bunny at the simple sound of pellets in their bag (she probably reminded of her time in the pet shop, where she had to get her food first or don't get any at all). So really, put all the chances on your side, and first of all, get both fixed! Then wait till they have become adults, because false bonding happens often with babies. Once they are adults, the bonding generally has to be redone because hormones kicking in changes everything.
It is said that a female/male pair will be easier to bond than same sex pairs, probably because even fixed, they will eventually form a couple. But I've seen pretty any kind of combination till now. And there are bondings that are easy and fast, others that take time, LOTS of time and efforts and different bonding methods till you find the right one (separating both for weeks and making them switch places for example every two days so that they get used to the other's scent, or 'stress' bonding, where you put both in a cardbox and shake it a bit so that the stress/fear make them bond faster. Plus other techniques). What you can do if you want more chances to find the best partner for your rabbit, is to go to a shelter and ask for a cal, already fixed, adult bunny. Then you can ask the staff to let you introduce them and see how they react to each other. You would also save a bunny from possibly getting killed. Just saying.
Good luck!