What is the most effective way of potty training a rat terrier puppy in an apartment?

Kathleen asked: The puppy is female, and 8 weeks old.

Housetraining Your New Puppy

Housetraining

No training is more basic for pet owners than that first important lesson: Do it outside!

Training your new puppy to potty outside the home, not in it, usually starts between six and eight weeks of age. Dogs as young as four weeks can be house broken, but at that age few [...]