I am by no means an expert. My family raised birds when I was a kid (pheasants, quail, chuckers, Canada geese, ducks, turkeys, and pea fowl... Haha no chickens) but I have been away from the farm scene for a long time. This spring I got some chicks. I didn't spend as much time with them when they were younger as I would have liked and found myself with girls that like me but didn't want me to touch them. After they were out of the brooder and in the coop, I decided to try and change that. If I may, I'll offer some tips that have worked out for me as a beginner.
1. Get a call. "Chick, chick, chick!" is common. I use "Hey, pretty ladies!" It doesn't matter what it is just be consistent with the inflection. It is your "cluck." A friendly way to say hello. I say it anytime I go into the coop or run and especially when feeding, watering, or giving treats.
2. Get them to be comfortable eating out of your hand. May not be great for little kids because they can peck hand-flesh through scratch. When instructing my friends on hand feeding I tell them to keep their fingers together. Chickens love that fleshy part between your fingers! Also, use your call when feeding them. It associates your "cluck" with treats.
3. Get a stool and just sit in the run. Use your call, imitate theirs. Be patient and gentle. Feed them from your hand sometimes. Sometimes just sit there. Eventually one might fly into your lap. It's so very tempting to try and pet them right away. Don't. Just let them check you out. Use your call (Hey, pretty lady... Or whatever) and let them explore you. If one flies up to check it out and goes well, chances are another will, too. After a few of these experiences, try to pet one. Away from their face, down their back feathers. Don't try to restrain them. I learned too late that a towel over your lap is a good thing. Poop smears on my pants were inevitable, and by the time I got savvy with the towel, I had to start all over again because the towel was "new." if I could do it over I would have two identical towels, one for my lap and one to switch out when it needs to go in the laundry.
Do all my chickens like to be on my lap? Nope. They are curious and will pop up for a minute or so. Some never do. I do have two that like to hop up for a petting. If I go to hold them? No way! It is nice to pet the ones that I can. They are my favorites, of course. Goldie Hawn and Audrey Hepburn.
Like I said, I am new to this chicken thing. If I could do it over, I'd do it different but here I am with what I've got. I hope this helps. Good luck!