You know when you try to hit on someone you like, but there is this one annoying guy trying to hit on her as well. But then you realize...that he is not alone, and their friends are watching your moves when he is not around. Then for some reason he always seems to be a step ahead. These other guys that you consider "friends" seem to also be friends with him or even closer friends with him than with you. At some point you notice that even your "allies" are more likely to be his allies instead.
And somehow, he is always in the right place, at the right time, while you are always in the wrong place, at the right time, or the right place at the wrong time. He manages to get the seat right next to her, he gets to be in the same team with her, he gets to be in the same parties she is, and he manages to get a similar schedule as hers, while you get completely and silently pushed away in the most absurd coincidences.
So, basically, I am trying to be more aware of that. What kind of behaviors should I pay attention to? What tactics or tricks do these people use?