If you want a dog that looks like Lassie but fits in your apartment, you might consider a Shetland Sheepdog. Shelties usually stand between 13 and 16 inches tall at the shoulder, though they can be as short as 10 inches or as tall as 22 inches. These dogs tend to be loyal and affectionate toward their owners, but may be reserved or even shy around strangers. To choose the perfect Sheltie for you, you'll have to decide what characteristics you're looking for.
Figure out whether you want an adult or a puppy. The advantages to having a puppy include being able to train your dog from a very young age and getting the chance to enjoy its cute puppy antics. An older dog will generally be mellower, better-behaved and less inclined to chew on random household objects.
Pick a gender for your ideal dog. With Shelties, there is very little difference in terms of temperament. However, if you already have a dog that dislikes one gender or the other, you may wish to take that into consideration when choosing your new dog.
Decide what size you want your Sheltie to be. Since their size can vary so greatly, you have a lot of leeway here. If you're living on a farm, you might want a larger dog, but if you live in a city apartment you might want a smaller one. If you're buying a puppy, the breeder should be able to guess the approximate size the dog will be as an adult.
Visit a reputable breeder and spend some time with his available dogs and puppies. Look for a Sheltie whose personality meshes well with yours and who will fit in with your lifestyle. You may be drawn to one of the energetic, romping puppies, but if you're gone for work for eight hours a day, a calm and mature dog may be a better match.
Ask the breeder questions. She should be able to tell you everything you want to know to help you decide on your future dog. If you're unsure, describe your lifestyle to the breeder and ask for her opinion on the best Sheltie for you.