One thing I always watched for, was any changes in behavior. Grumpy, stomping feet, biting at sides, mother of dragons etc. I meant to ask, will she be foaling inside or out ? If she will be foaling outside, have a look at where she is standing a lot of the time. Usually as a mare gets closer to foaling she will be hanging around where she is going to foal. ( not always the case, but has happened a few times over the years)
Theres heaps of pinned threads at the top of this section of the forum. Nows the time to be reading them whenever you get a chance. Foaling kits, red bag deliveries and what presentation you need to be looking for as to distinguish if something is wrong.