At the time I was bringing home an 8-week old basenji male into a house with an 8-year-old basenji female. The most practical advice I got was from the breeder. The breeder stated that I should introduce them (given the known issues I had in the past with my girl not permitting other dogs around her things) by walking in the door, setting the puppy down and immediately going over to my 8-year-old girl and greeting her in the normal manner. It helped that my good friend was at the house and keeping her occupied. My new puppy eventually found his way over to us and although she was startled to see him, she went to him, smelled him and then played with him.
The bottom line is that her advice was to make the situation as nonchalant as possible. And it worked. They have become the best of friends... mostly