The comb gets redder and they will often squat down (as to accept being mated) as you walk up to them. They should get more interested in the nests. Many put golf balls in the nests, which seem to say to he pullets, this is a good place to lay. Anything you have that looks more or less like an egg is fine. You can fill plastic easter eggs with sand or dirt and use them; you can even use rocks of the general shape and size. They tend to like a darker nest; you can tack up a strip of cloth across the top part of the opening to darken the nest somewhat. Some people lock them in the coop during the first part of the day or til their eggs are laid.
It usually takes them about a month to get the whole egg laying thing right. Before then, you might see soft shelled or misshapen eggs, very small eggs (even without a yolk,) an egg laid from the roost or just dropped in the run -- different things.
I've never found I needed to do more than put a golf ball in each nest and wait for them to get it right.
