Our cat was 7 when we brought home our labrador. She was a year old, so pretty big already and intimidating for a small cat. Wherever the cat was hiding, I would bring our dog nearby and have her lie down, and talk to the cat (I'm sure I looked like an idiot). Over the week, I did this closer and closer to our cat. I would also bring our cat over when our dog was in her crate and hold her there and pet her and talk to them. After about a week, the cat roamed more freely around the apartment, though still not comfortably, until she learned the dog was not going to harm her. They never became best buddies, but our cat became very comfortable with our dog (later in life she would lay on our dog's bed so our dog couldn't get on it, and I even caught them laying together a few times). Because your puppy will be smaller, she may not be as intimidated, but puppies are also bouncier and less predictable. Cats almost always put up a fuss to show that the house is their territory, but they will get probably get used to each other naturally without all the crazy transition stuff I did!
Also, I have to respond to Laura by saying shelter dogs are a great choice, and I would like to know where you did your research about lack of pet overpopulation. A huge number of shelter dogs are there because kids wanted dogs and did not take care of them, or people had to move and couldn't take their pets with them, or the dog got bigger than expected...Shelter dogs are the best! They are so appreciative of a good home, and though some have behavior problems, it is almost always due to lack of attention and training and this is very correctable with a patient family. I could go on about they benefits of shelter adoption, but that is a whole other posting!