Chickens are notoriously difficult to catch, but you can just stuff a bucket full of treats and wait for them to stick their heads in. Then grab them while they're blind. Particularly useful with selfish roosters and chickens, who will try to hog all the treats.

It'll only work once though. After that, they'll keep an eye out on how close you are before they stick their head in. If you're seriously gonna use it, you should give them treats in the bucket often, to lull them into a false sense of security.