Slow and Go
There are some dogs you can let right in the front door, pop off the leash and it's all fun! You will learn how your dog is going to react to new fosters quickly. I would recommend slow intros until you know how your dog is going to react to the new dog as well as how the new dog will act.
I agree with the first meeting on neutral territory. Take them on a walk together with a different person holding each dog. Pointing them in the same direction instead of facing each other gives them the same goal and can reduce competition. Slowly bring them closer together to see how they do during the walk. Some dogs are great off leash, but aggressive on leash, so if one of them gets snippy on the walk, that doesn't mean you've failed.
Once in the home, I'd crate the new dog and let your dog visit him through the crate. Trade off and crate your dog so the new dog can smell her. Again, some dogs get barky when they are crated and another dog isn't, but this is a new learning experience for your current pet as well as the new foster.
Once you get to learn how your dog reacts, each meeting will be easier, you'll know what works and what won't with your dog.
Here's what works for me....
When I get a new foster, I crate all dogs and let the newbie outside to go potty and check out the yard. We have a pool, so I make sure that s/he doesn't fly into it!
I put a leash on newbie and let out my most mellow boy. Archie normally ignores them but I let newbie smell Archie. Archie is very non-threatening so I get newbie used to a dog that isn't all in it's face. I will let newbie off leash if I see a playful attitude from him....but I will always be within a collar's grab. Being by the pool is helpful in case they have a fight, there is water nearby.
I will then let out Spanky. He's a GREAT dog park dog, but very nudgy one on one. I will put both on lead to let them meet. Spanky is also a dominance humper, so I will normally leave him on leash while I let newbie off.
I will then let out Dixie, our alpha female. She is VERY bitchy when she first meets the newbies, so she is on lead the longest. There are times when she or the newbie (if female) will be on leash for a week while they are in the home together. Usually after one week she chills out and will start to play with newbie.
I always err on the side of caution. Until I'm 100% that I can handle the dogs without an extra pair of hands, I will ALWAYS have one leashed to me to prevent or correct any unwanted behavior. I also have babygates to certain rooms to make sure that the newbie is contained with me (to prevent potty accidents) but can see the other dogs. This is primarily in the 'toy room'. I don't trust newbie with toys and my dogs until after the first week. During this time I can see if newbie is a toy hog and how possessive s/he may be.
I wouldn't recommend any types of rawhide or bones with newbies as this is a MAJOR cause of fights. Dogs can really go crazy when rawhide is in the room!
Sorry for the rambling...but the slower the better! You'll LOVE the feeling you get by saving a dog's life and it's SO much fun having multiple dogs in the house!
Thank you for opening your home and your heart and fostering!
