It's best to introduce dogs on neutral territory such as a park. However, introductions on neutral ground don't always indicate there won't be any problems intitially. Our pomeranian and our yorkie and our pomchi were introduced in the play room at the adoption center where we got the pomchi. The yorkie and the pomchi got along fine while the pomeranian ignored him. We went ahead with the adoption. When the pomchi was delivered to our home it looked like things would go smoothly. However, after the woman from the shelter left and when our yorkie and the pomchi were having a grand time playing - our pomeranian attacked the new arrival. The pomeranian considers herself to be queen of the house and how dare this newcomer invade her territory including playing with HER pal. She attacked several times unexpectedly out of jealousyfor awhile. After 3 years, she attacks less often, but the pomchi has lost all trust in her although she now makes friendly overtures toward him. At this point they tolerate each other.
Our most recent adoptee in May was a chihuahua that our dogs used to meet on their walks in the neighborhood. The chi was a stray that was taken in by a family that couldn't keep her so they brought her to us. Although they seemed to get along previously, there has been strong competition between the chihuahua and the pomeranian with the same conflicts as before. The only difference is that these two dogs have the same "QUEEN" attitude.
Even when the introduction setting goes well, it's not always an indicator of how things will go at first. It all depends on how much you want both dogs and what you will do to help them to at least grudgingly tolerate each other.
Beverly