I spend a lot of time with my chickens, more so than with my previous chickens, and I've noticed things that I didn't know before. In chronological order, here's what led up to laying. Combs reddened up, some to a striking red, some still pale, but red enough. Rooster started to take notice, in order with the comb reddening. Fluffy butts! Their rears dropped lower, giving a fluffed up look. Quite noticable on birds of the same breed between laying and not laying yet. Increased water and food intake. Nesting about 3 days prior to laying, practice setting, perhaps. Day of, more time spent on nest, or pacing the hen house and cackling, as if "lost" and unsure of where to put the egg. About 2 hours after pacing the egg appeared in a nest. 2 of them did this, the other 2 made no ceremony of it. Eggs arrived a week to two weeks after the first "symptom". There is one that hasn't started yet, her comb is as red as the other, rooster "likes" her, but her butt isn't fluffy yet. Palpating before the fluffy butts and after let me know what I was looking for there... the "hip" bones? The pointy ones under the tail, they spread apart. Real skinny width in a non-laying pullet, they more than double the width between those bones when laying is going to start happening.