When putting up dog fencing, there are a number of considerations to account for. Is the system you're using humane? How athletic and aggressive is the dog, and are you concerned about keeping other dogs out, too? Does the dog tend to chew? Let's explore some of the issues you'll want to address.
Humane Solutions
People often lean on solutions that are far from humane. If there's anything that uses pain to "teach the dog a lesson," it's inhumane. This goes for any form of electrical fencing or so-called invisible fences where dogs are shocked when they breach certain perimeters.
Since humane solutions matter, you want to avoid anything that could harm the dog. All electrical solutions are out. Similarly, anything like barbed wire could snag the dog and cause harm. Focus instead on using products made of wood, vinyl, polymers, or plastics.
The Dog's Activity Level and Aggressiveness
Take a look at how high your dog can jump when you're just playing around. Whatever that height is, you want something at least two feet higher than that. Why? However motivated your dog is when it's playing, it's going to be a lot more energetic when there are worries about ever-deadly intruders like the postal carrier.
Know the breed, too. Work dogs and terriers can be surprisingly good jumpers even if they're old and heavy. Ask other people who've owned dogs like yours about their experiences.
Dog fencing is about more than keeping your dog in. Yes, it might seem laughable to put up an 8-foot fence if you have a wiener dog. The question you need to ask, though, is whether there are neighborhood dogs to keep out. If your next-door neighbor has a German shepherd, for example, the fence isn't just there to keep your small dog at bay.
Chewing Habits
Some dogs are aggressive chewers. If they are, then you want to verify that any dog fencing products you use are safe for use around such canines. Avoid using plastic and polymer fences that weren't designed specifically for use near animals that chew. Don't substitute farm animal fencing, either, as it's often designed to contain herd animals and not an athletic apex predator like your Chihuahua. This is especially worth worrying about if you have puppies around.
Take a look online on sites like http://www.4cornersfencingco.com to see what types of dog fencing is available and what would work well for your dog.