One of the most important things about exuding an air dominance is being able to remain stoic and appear collected. As I've mentioned before, boys are naturally inclined to try and steer a scene to make it more pleasurable (or at least less unpleasant) for them. Whether or not it's conscious isn't relevant for this point, but remembering they behave that way is. In order to do this, they have to be able to see some of what's going on inside a Dom's head.
Anyone who's ever owned a dog has likely had an experience where their dog will listen to one person exceptionally well and won't listen to another person at all. My old dog training mentor used to say "I love dumb dogs, they're easy to train; it's the smart ones you have to watch out for." In this scenario, the person who can't get the dog to obey probably thought it was just a dumb dog. The reality of the situation is that the dog observed the person's behavior, realized they were full of shit, and decided that if they were lazy and didn't obey that nothing bad would come of it. And you know what? That dog was right - if that person had been playing poker with that poor of a bluff they'd have lost their shirt.
Now, back to boys. The same sort of principle applies to boys; they're going to learn what they can get away with based on how a Dom responds to their reactions. Sometimes it really can be emotionally taxing to push a boy in certain circumstances, and this is a good portion of why it's important to remain stoic. If you can't mask your emotions and instead respond immediately to a boy's reaction, he's going to learn that the faster he reacts that way the faster you'll stop. If you've ever had a scene where a boy becomes significantly more sensitive to various repeated stimuli as a scene progressed, this unconscious conditioning is a possible reason.
I write this as someone who has experienced this concept from both sides of the equation, so I absolutely understand what it's like to be pushed too far. In those instances where I have been pushed that far, it's much more useful if after realizing I can't handle it the Dom persists for a short while. Why? Because it means it's on his terms and I'm helpless to affect (well, deter) his actions. By deliberately hiding your thoughts and feelings from a sub, he can't do what that "dumb" dog did and learn your behavior.
In addition to remaining stoic for purposes of preventing a boy from knowing when you're distraught, it's useful to keep a calm demeanor which is also devoid of excitement. If a boy can't read good or bad responses from you he's going to be in a constant state of distress where he has no idea what the hell you're thinking. If he senses your excitement, he'll know that you're clearly pleased and either that he should persist or that you'll cut him some slack because you're happy.
Finally, though it sounds like it's out of some book telling women how to get men, it's usually not a good idea to chase a boy. Of course this is different for a more casual dynamic, but if you're going for serious power exchange it's starting off on the wrong foot. It's a bit of a fine line to walk, as there's always a risk of imposing expectations of the wrong level of trust on a boy, but it's still an important part of establishing a dynamic. Just as I've advised subs not to feel pressured to make every Dom feasible for play, the inverse is also true for Doms. Basically, if you're chasing a boy before the scene even starts he's going to already know he can play you like a fiddle. This doesn't mean you should just treat a boy like shit in scene negotiations and expect him to deal with it, but if your goal is power exchange a boy should feel like his absence in your sex life would have absolutely no impact on you at all.