Click for Calm
Start by simply clicking your dog for calm behavior. I know, I know, I can just hear everyone say but how do I get my dog to even exhibit calm behavior so I can click them!?! At first management will come into play - find a spot to sit down and have your dog on a leash next to you. Ignore them and only click and treat when they decide to lay down. Try not talk to your dog when you reward them, you don't want to build arousal. Do several short training sessions every day and try to time them for right after an exercise session when your dog is tired anyway. At first you won't get long stretches of calm behavior and that is normal :). This is a gradual process. As your dog gets better at being calm for longer periods, be sure to reinforce randomly - sometimes for shorter pauses, sometimes longer. When your dog will remain calm for several seconds at a time, you can start adding a verbal cue. Over time you can phase out the click and treat and instead use other rewards such as calm praise or a gentle massage.
Here is another great Youtube video of this by my favorite Youtube trainer: CLICK HERE
Relax on a mat
Another variation of click for calm is to teach a go to your spot behavior. Whole Dog Journal printed a great piece detailing how to teach this so I will let them explain it :) - CLICK HERE. I love the go to your spot behavior and I teach the foundation of it in all my beginner classes.