Most hens get "nesty" before laying eggs. Taking shredded materials to a place and making a pile or heap, or finessing the material to create their nest. Sometimes they can guard that space, and if you go near they may hiss or stand with their head bowed a little and an open beak.
You may also notice more cavity seeking when out of the cage, exploring your home looking for nooks, possibly guarding them. Maybe going inside your clothes, another cavity seeking behaviour.
Some hens sit in the food bowl, others find a nook in the cage, others use the cage floor in a corner.
All traits will vary species to species.
The give away in the day before an egg is the notable egg-shaped bump down under the birds tail. The egg shell is created around the egg and then it is laid within 24 hours. So laying time between eggs is then about every 24-48 hours.
Are you noticing any abnormal behaviours?