Women say they resent it when men tell them to smile. And well they should. An instinctive smile, when one is not expressing pleasure or recognition, is a submissive gesture. This is why attractive women tend to smirk in response to the big goofy submissive smiles sent their way by lower status men.
One easy way to increase your perceived level of alpha is to simply not smile at strangers. Instead, just reply with a nod or a pleasant word. One can be perfectly civil without grinning at everyone like an idiot, and it's always interesting to see the difference it makes in people's perceptions.
I'm not talking about walking around glowering; self-conscious anger is much worse than indiscriminate smiling. But women have always been drawn to brooding men, so rather than turning them away with a gesture of preemptive submission, give them something to which they can be drawn.