Your border collie is already herding the cats, visiting children and guests at your parties. That's his nature. and he's very good at it. Make your dog happy by allowing him to do what he does best, and have a good time yourself, by learning the basics of herding.
Herding simply means moving livestock from one place to another in as efficient and stress-free manner as possible. That's the definition, but it's easier said than done. You'll need to find an instructor. As the United States Border Collie Club notes, "An inexperienced handler working with an inexperienced border collie and inexperienced livestock can end in injury to at least one of the three species."
Most people want to train their border collies themselves. That's fine, but you should find an instructor to teach you the basics and keep tabs on you and your dog's progress. You also need access to sheep or other livestock. Depending on where you live, you might have little choice in the instructor department. The Border Collie Society of America advises that facilities and equipment are important factors. Without the proper pens, fields and arena, it's difficult for a young border collie to progress in his training. If the instructor only has a few sheep that know the whole process inside out, once your dog develops the basics he'll need new livestock to work on.
Before training your border collie for herding, make sure he's obedience-trained and responds quickly and consistently to your commands. You can take him to a local obedience trainer for this. He'll need the basics: Sit, Stay, Down and Come. He must walk well on a lead and be trustworthy off leash. Since border collies are smart, he's likely to soak up this training in no time.
After you've gotten obedience training down, you can start with basic herding training, including voice tone. The United States Border Collie Club points out that tone of voice is extremely important. To get your dog to move faster, use a high-pitched, quick tone. Slow down means a lower pitch and dragging out the command. Correct your dog in a low voice with a growly edge. To improve your dog's attention, speak in a whisper. The USBCC recommends a conversational tone for other border collie work. Your dog must also learn that "Away" means moving livestock counterclockwise, while "Come By" -- or a similar term if you don't want to confuse your dog with the basic "Come" -- means to move them clockwise.
You don't really train your border collie to herd -- that's instinctive with him. You train him to respond to your direction when he's herding. While herding livestock, your dog looks to you for cues. The USBCC advises that to bring your dog toward you, move away from him. To move him away, go toward him. "Take two steps backwards and hunker down to pull a border collie all the way to you," the USBCC says, adding that your emotions should show through your eyes to your dog's eyes. If you're disappointed in your dog, look at him, then immediately look away. If your dog stops paying attention, throw your hands up, then walk away. Most dogs come up to you, wanting another chance. Go through the situation again, using a leash if necessary so your dog gets it right.
Once your dog knows all his obedience, voice and movement training, you put this to use by having him work livestock. He'll learn penning, which means putting sheep into a pen; separating, or taking one or two specific sheep out of the herd; driving livestock to and from his handler, and driving livestock through gates and other impediments.