I was recently asked how I keep my dog from chasing wildlife on the trail.
I will begin by stating that I do not propose to be anybody's expert or authority, so don't attack or bash me if you don't agree.
I solve the problem of "chasing" the same as for many dog issues. My answer is a ROCK SOLID RECALL.
I won't try to describe the details of achieving this because there are entire chapters, maybe even entire books on just this. Discussing training theory and techniques will take forever and open all kinds of "cans of worms". And it may be different for each dog.
One suggestion might be to find a local training club to work with. They can be very beneficial. There are also many books and DVD's available, but I think a good obedience club gives you the best advantage.
I have many commands, of coarse. But the "recall" is, I believe, the most valuable command one can have (by recall, I mean: COME, HERE, or whatever you use). Here's why.
One of the best ways to stop unwanted behavior is to substitute some other, acceptable behavior. For instance, if you want a dog to stop jumping on someone, substituting a "SIT" will solve it easily, without resorting to aversives. The dog simply cannot jump and sit at the same time.
A "recall" can be used to stop or prevent many unwanted behaviors on the trail such as running up to strangers, chasing wildlife, stepping on peoples sleeping bags, stealing or begging for food, getting other wet & muddy, going in the road, fighting with other dogs, scaring horseback riders and cyclists, etc. I always say that if you can call your dog to you, reliably, it will stay out of trouble. You may also find that your dog will be welcomed and embraced a lot more.
Or coarse you must clearly define what a recall is. I expect my dog to come and sit, in front, facing me, close enough to touch me. I also have a "HEEL" which means sit on my left side, or walk on my left side when I move. For most pet owners I think coming close enough to take hold of the collar is good enough. But I recommend that the dog sit because a dog is less likely to "break" away once it is sitting (more reliable).
The most important thing about training and maintaining a reliable recall is to never make the dog sorry it came to you, always try to make it glad it came to you. That means frequent rewards for coming, and never, never, never "correct" (punish) a dog after it came to you...no matter how angry you may be at him.
Of coarse there will come the time when he will disobey. And training to a level of reliability among all kinds of distractions can be quite a challenge. That's why I recommend an obedience training club. One where they are training for competition, if available. They usually have several trainers and members to help, and prepare there dogs for distractions. You don't need to train for the same precision, necessarily. But it's about RELIABILITY. If you can achieve that, you will be proud and confident to take your dog anywhere. You problem will then be fielding all the questions about how you got such a good dog!