Depending on the situation your dog can have an extremely short attention span. And in those situations, often times we humans are asking our dogs to jump through hoops. Okay, maybe not literally jump through hoops, but in a situation where we can barely get our dog's attention, the last thing that we need to be asking for is more advanced things like sitting or lying down.
The first skill that needs to be worked on is a cue that gets the dog to look at the human. This is often referred to as a "watch me" cue. This is the first thing I recommend teaching to your dog. I don't currently have a video on it so I will do my best to explain it. Firstly, start teaching new cues in your own home. Do this in a room that has limited distractions. (eg cats, dogs, other humans etc.) Start off by taking a small piece of food that your dog finds enticing and bring it to your dog's nose. From there, take that piece of food up to your eye and wait for your dog to make eye contact. When he does, tell him "good" and give him the the small food reward. Do this a handful of times until your dog is really getting it. From there, you're ready to move onto the next step.
The next step is getting this new behavior on a hand signal. For this, you will mimic the same motion you made with the food, but without the food in your hand. Basically, you'll point at your dog's nose and then up to your eye. Once your dog follows your finger and looks into your eyes, tell him "good" and then give him a small food reward from your treat pouch. Do this a handful of times until your dog is really nailing it. From there, you're ready for the next step.
The next step is adding a verbal cue for this new behavior. I say, "watch." To introduce this new cue, say the word, "watch," wait a few seconds, and then do the hand signal that you previously introduced. Reward your dog for following the hand signal. Do rep after rep and before you know it your dog will be looking into your eyes when you say the cue, "watch."
Why did I go into such depth on how to teach this behavior? Because this is what you really need to be working on if your dog is easily distracted. Teach this to your dog in your home in a room that has limited distractions like I mentioned above. From there, teach this to your dog in the back yard, and then the front yard. Start off at the very first step when starting in a more challenging environment if your dog needs it. The end goal is to get your dog to respond to the verbal cue in any environment.
Here's the takeaway:
This will make your life a lot easier. To make this successful, do lots of reps with lots of reinforcement. (Reinforcement in this case means food rewards.) If you pay your dog, your dog will continue to work for you. Just make sure you're using something that your dog really enjoys. Working on a very solid foundation of a watch cue is the place to start. If your dog is looking into your eyes, he's not looking around at everything else.
"Watch" as taught by Jean Donaldson, The Academy For Dog Trainers