Below is some great info from Pit Bull Rescue Central on how to introduce your pit bull to another dog. Visit their website for more great info if you or a someone you know owns a pit bull.
Parallel leash-walking, on neutral territory with two handlers, is a great way to introduce dogs. Neutral territory means an area where neither dog has been or where neither dog resides. An unfamiliar, neutral territory is best to avoid territorial behavior in either dog. Both dogs should be wearing properly fitted collars and be on nylon or leather leashes. Prong collars, choke chains, and Flexi-leads should not be used when introducing pit bulls.
While taking a short walk, allow the dogs to curve around in a natural manner. (This is a strategy encouraged by trainer Turid Rugaas, author of “Calming Signals”). Both handlers should have a firm hold of their leashes, however, they should try to maintain a U-shaped bend in the lead. Taut, tight leashes may communicate tension to the dogs and should be avoided if possible. Avoid face-face, head-on introductions between dogs. Instead, walk parallel to each other, a few feet apart, and alternate which dog is ahead of the other. Also, do not allow a dog to greet another dog if he/she is dragging you towards the other dog or is misbehaving in any way (pulling, jumping, or lunging). Doing so will result in training the dog to misbehave to gain access to other dogs! The dog does not make the decision as to whom he will meet and when. You do!
If the dogs appear to be friendly to each other, allow brief sniffing with one dog perpendicular or “T-shaped” to the other, and then each dog should be called away by the handlers. If either dog stiffens, stands up on its toes, or shows any aggressive posturing, call the dogs away immediately and interrupt the interaction. It is important to interrupt before things go wrong so that you can preserve the possibility of a successful interaction at a later time. It might be necessary to take several walks, in different locations, over time. Multiple introductions in this manner give you a better read for how the dogs will do. Do not rush this process if the introductions seem ‘iffy’ in any way. Stop the introduction if either dog is showing signs of fear or aggression. Body language that indicates fear or aggression can include: raised hackles, stiff posturing, lip curling, growling, air snapping, tail tucked between legs, one dog avoiding the other or wanting to hide behind the handler, lunging, or freezing.
If the leash walking is successful, it may then be appropriate to go to a fenced area and have one dog on leash, and one off. One handler might work obedience with the leashed dog, while letting the other dog roam around, allowing them to get used to each other’s presence and scent. Usually in this scenario, the resident dog is loose, and the new dog is leashed. This gives one dog the ability to safely check things out and move away as needed while you maintain control of the other dog. Make sure the yard or fenced area is free of items that may possibly trigger a fight such as high-value toys, bones, rawhides, etc.
When introducing dogs on leash, make sure that the leashes do not become tangled. Entangled leashes can increase tension and result in a conflict between dogs.