Agree with Blue Eyes, bunnies don't ask for affection the same way dogs do. They're a lot more subtle about showing that they like you, and how they do it depends on the individual rabbit.
A big part of bonding with them is simply demonstrating that you are not a threat to their safety. Rabbits are prey animals and it's their natural instinct to be afraid of anything that looks big enough to eat them. Holding them in your hands, to them, is very much like an eagle catching them to kill and eat! That can be very scary and should not be forced on your rabbit until they trust you. Rabbits like being on the ground, it feels more natural to them. Just spend lots of time with them passively, read a book or just watch and talk to them. Don't chase them, or touch them unless they approach you. Let them get used to you being there and being a friendly presence that wouldn't hurt them.
Another big part is food bribery! Rabbits can be very food-motivated. It definitely helps to associate you with yummy yummy goodness. When it's feeding time, you take the bowl out of the cage and sit by it and fill it pellets so they have to come to you to eat. Talk to them a lot so they associate your voice with good things. Same when you feed them treats, like bits of banana or fresh herbs. I say "Come here come here!" in a high pitched voice whenever I have food, and now my bunnies come flying towards me whenever they hear it.
Building trust is just a matter of paying attention to your bunnies' comfort level and building your own unique relationships. Here's two of mine for an example.
Sasha lets me know she loves me by coming to where I sit and stretching out on the floor, letting me pet her. As bunnies are prey animals, you can tell their comfort level by whether they are in position to bolt. The more out of position they are, the longer it would take for them to get up and run if a threat appears. Stretching out on the floor shows she feels very relaxed and not threatened by me, a predator animal 50 times her size! That is a huuuuge amount of trust, and it's one of the subtle ways a bun shows that in her eyes, you're okay.
Merlin is a tough one. We have a very antagonistic relationship, mostly due to the fact that he is a stonking brat. He nips me quite often when he's moody. He doesn't really let me pet him. But somehow, I always find the little tosser bouncing around wherever I am in the house. If I'm watching tv in the living room, he's sniffing around my butt and jumping into my lap only to jump off angrily when I try to pet him. If I'm in the kitchen, he's stepping on my feet hoping for food scraps. If I'm in bed, well looky who just jumped up to see what I'm doing. He's just always around me, wanting to be near me, just not wanting to be bothered by my grabby paws. That's just how he is, that's his comfort level, and that's fine by me.
Every bunny is different, and that's why they're so special to us.
