If you've ever searched for how to get your dog to pay attention, you've probably come across the same advice over and over again. Teach a "watch me" cue. Say your dog's name. Make noises. Wave a cookie. If they look away, find a way to get their attention back.
There's nothing inherently wrong with any of those suggestions, and there are certainly times when they're useful. The problem is that they don't answer the question I think matters most. Before I ever ask my dog for a sit, a down, or a heel position, I want to know whether they're mentally available for learning. Instead of asking, "How do I get my dog to pay attention?" I've learned to ask a completely different question.