In my opinion the best way to introduce two new dogs is in an unfamiliar place, to them both. This way, neither of them should get territorial. The biggest mistake I see people make is walking the two dogs straight at one another on leashes. This is extremely confrontational. It's not wonder the dogs end up fighting! It is best to just start walking together, side by side. This way the dogs can sniff one another, get to know each other and get some good exercise doing it. Walk and walk until the two dogs are all tuckered out. (Too tired to care or get grumpy.)
Now you can head home. The dogs should just want to lay down for a bit to rest, and by the time they become rejuvenated, they are old news to each other.
Now sure, things don't always go as planned, but just remember not to get mad or upset. You must have patience and you can try again, but also, know when to quit.