Here is a great site by Debbie Jensen that will tell you everything you need to know:
Canine Reproduction Video and Book on Breeding and Whelping dogs by Debbie Jensen for dog breeders and Whelping Supplies needed to deliver puppies.
Be sure you have a quiet, dark safe place out of the way of foot traffic for mamma to whelp. Youll need some kind of whelping box for her and the pups to be for at least 10-12 weeks.
Visit garage sales, second hand stores and your local good will stores to get baby blankets, rugs, towels or anything that is washable and can be used for bedding. You'll go through a lot. Start saving news papers you also need lots of those. Look on the site I gave you for your whelping supplies. You never know when you may need to give mamma a hand if whelping gets drawn out. She may tire easily during birthing and cleaning the pups.
It's important that she be eating puppy food for calcium intake and milk production. Try getting the same brand that she eats now. MIx a scoop of dry puppy food with canned puppy and some water. She should be eating 4-5 small meals a day up to and until the pups are weaned.
Start putting money back in case she needs to have an emergency c-sec. Have your vets number and the emerg vets number on hand. If possible get her x-rayed to verify the number of pups she is having.