Diet - During the first 30 days of pregnancy she can eat her normal diet, as long as it is a high quality food. During the last month of pregnancy start switching her over to a high quality puppy food, make the diet change over a weeks time. Do not give vitamin supplements, a high quality food has plenty of nutrients. Also, be aware that some vitamin supplements may cause birth defects so check with your veterinarian before choosing to supplement.
Exercise - Take her on daily walks. It is important that she does not become overweight during this time and the walks will keep her in shape for delivery. Letting the dog run in the backyard is not equal to a walk, a walk is mental and physical exercise. During the last 3 weeks of gestation do not take her out and do not expose her to other dogs as added protection against disease.