Australian Cattle Dogs are a HERDING breed
This means (in real life) that they are TREMENDOUSLY active, interested, and are frequently smarter than you are. Seriously.

Why do you want an Australian Cattle Dog? What are you looking for?

ACDs wind up in shelters because their owners "thought" they could handle an active breed. The dogs pay for the owners' lack of self-knowledge.
If you want a dog that will go lay down while you're busy making dinner,
THIS IS NOT THE BREED FOR YOU.

If you are not a FIRM, CONSISTENT dog owner, this is not a good breed choice. Cattle dogs will rule the roost if given 1/16 of a chance to do so.

They shed (called "blowing coat"). You can knit a new dog from a good week of coat-blowing. Coat-blowing is at least twice per year per dog, and lasts for roughly six months at a time.

You might read they are a "quiet" breed. That depends on the dog; we have one who narrates his entire life. This is less fun than it might sound, although we're accustomed to him now.

Why are they commonly known as "heelers"? Because they were bred to herd stock by "heeling" - nipping at the heels of the animal. "Nipping" means use of teeth. Guess what else they nip with teeth! You. The vacuum. The rake. The snow shovel. The lawn mower. The car. A neighbor kid on a bicycle or roller skates or a toddler running past. Unless you train them not to (see above paragraph about owners "thinking" they can handle this active breed, and you can project the amount of success many people have)

An excellent book on the Australian Cattle Dog history and breed development: A Dog Called Blue by Noreen R. Clark

You have to be prepared to handle a cattle dog. If you don't have the time, the energy, training skills, and the patience, do not get an ACD pup or young dog (an older dog might work for you, though, there are some great older ACDs who need homes).

Oh - and heelers should have their tails. No docking!!