Once an egglaying female is about 5 months old I recommend that you provide a suitable place in the cage for her to dig in case she needs to lay eggs. That way you shouldn't have to worry about when exactly she will lay the eggs.
The container needs to be opaque and at least big enough that when empty she can fit into it with at least 2" to spare on all sides of her including above and below. I use washed playsand and fill the container at least 2/3rds full.
Once the female starts to dig in the container the sand should kept moist enough to hold a tunnel....and its very important that you do not let her see you watching her when she's digging. It will make her abandon the hole and can lead to eggbinding.
When she is getting ready to lay eggs some of the things to watch for include roaming the cage (looking for a site to lay in), drinking more, gaining girth in the back half of her body and near the end she may stop eating (not all of them stop eating though).
I also recommend that you watch her diet and don't overfeed her so that she will hopefully lay a small clutch when/if she does lay eggs.