Hi there our pups will be 3 weeks tomorrow and I can tell you it is a wonderful thing
My experience (and I am not an experienced breeder this was our first)
Didn't change her food just fed her more and added some cottage cheese
She went out for walks up until the last day really and just slowed down rather than bounding away as usual
Ate a biscuit on the morning she gave birth then didn't want normal food
Could not stay out of the garden, agitated and pooing (small sloppy ones) for about 3 hours before she took herself into the whelping box and refused to come out
Gave birth with no problems, had to help one pup hlf the way out and one leg of another otherwise all OK
She ate everything that came out of her except the babies - ugh!
Being longhaired it was hard to clean her bits up but she did sort herself out overnight
After she had the babies we had to really encourage her to got out for a wee, lead on as soon as her front feet were out of the whelping box
Fed & watered her in the box since she didn't want to leave
Contrary to what everything tells you - she did not want the puppies touched or moved for the first several days, got very stressed about it so we had to leave her alone with her newspaper bed and not touch it or them at all - OK tho' it doesn't smell
Wish we had waited another day to have the dew claws off - for her sake not the pups
Definitely wish I had had one of the whelping mats (2 in fact) from 'newdog' before she gave birth as she wouldn't have been able to dig it up
Glad I got the biggest whelping box I could for after the first week
Didn't need the heat mat - pups moved away rather than to it, probably the time of year
I know we had it very easy but don't panic and take things as they happen, have the phone number handy of someone who is experienced as a breeder so you can ring them if you are at all concerned and they will tell you if things are normal or not
Can't think of anything else at the moment
You should be able to start seeing tiny little flutters as the pups start moving and then you will start to see definite kicks and then be able to feel them
Good luck and enjoy the experience