It is going to be a little different dog to dog, most have a strong prey drive. If they see it, the go right after it. Kind of the polar opposite of a pointer.

We sometimes work up to thirty dogs together, mostly retrievers, pointers and general gun dogs. A Terrier or two is nice to have along, they are really good at flushing game, stay busy, stay motivated and can get into tight spots in the brush and thickets. The down side is they mess with the Retrievers and constantly try to steal the game from the Retriever. Calling them off of a hot scent or a chase is pretty much an exercise in futility. Many suck at at coming when they are called and tend to wander back when they feel like it, not all, but most.

You can avoid a great deal of grief if the Terrier is the opposite sex as your dog. Mine in particular (the two females) and others I've seen tend to hold a grudge which can last years (forever). Male female match ups tend to work better and fight less.

Been my experience any dog can be trained, Terriers are harder than most to train in general. They can be really stubborn and are prone to being independent.

One of the biggest complaints I've read on some of the Terrier boards is "my dog won't come when I call it". I trained mine with cheese. Some people have to lay on the ground and play dead to get their dog to come back.

A buddy of mine has a Patterdale or Patterdale mix, it killed a 50 lb. Doe in nothing flat. Doe decided to hunker down and hide instead of running away, big mistake.