Prong collars (also called 'pinch collars') are a series of chain links with blunted open ends turned towards the dog's neck. The design of the prong collar is such that it has a limited circumference unlike slip collars which do not have a limit on how far they can constrict on a dog's neck. The limited traction of the martingale chain combined with the angle of the prongs prevents the prongs moving close enough to pinch. The collar is designed to prevent the dog from pulling by applying pressure at each point against the dog's neck.
Money. Therein lies the rub. One of the drawbacks to training competitively is the cost. Between class fees and trial entries, this can be an expensive sport. That doesn’t have to deter you, though. Many clubs offer significant discounts on training and entries if you work at their trials, which was a huge help for me. I earned quite a few free or nearly free classes by working trials. The fees for junior handlers (-18) are also considerably more affordable.
Prong collars must never be turned inside out (with the prongs facing away from the dog's skin), as this may cause injury against the body and head.  Plastic tips are occasionally placed on the ends of the prongs to protect against tufts forming in the fur or, in the case of low quality manufactured collars with rough chisel cut ends, puncturing the skin. Like the slip collar, the prong collar is placed high on the dog's neck, just behind the ears, at the most sensitive point.
Head halters are an alternative to collars that works similarly to a horse halter. The halter fits over the dog's snout and behind its head (leading it to sometimes be mistaken for a muzzle). Halters reduce the dog's ability to successfully pull on the leash, but do not eliminate it. If the halter is used with a sharp jerk on the leash, neck injury to the dog may result, but used correctly head halters have not been shown to cause harm.
It's a good idea to proof your dog's training in different locations to prepare it for distractions. Invite a few friends over to cheer on your dog so it gets used to a crowd. You might also want to go to a training center or find local trainers who also have the obstacles set up in their backyard. If your obstacles are portable, you could even take them to a park.
Dogs that demonstrate the previously mentioned basic skills, as well as walking reasonably well on a leash and a few other minor tasks, can be tested for and earn the American Kennel Club's (AKC) Canine Good Citizen certification. While not a competitive obedience title, a CGC certification demonstrates that the dog is sociable, well behaved, and reliable in public settings. Some insurance companies will waive breed restrictions on dogs with CGCs, and many states have passed resolutions supporting and encouraging CGC certification as a yardstick for canine manners and responsible dog ownership.