Lots of the time a person seems to convey one idea but is actually trying to make you take away a different point entirely. With practice it’s easy to delve below the surface and understand many of the ulterior motives of those around us. But in order to do it we need to understand what motivates them and we need to stop taking words at face value, which is harder to do in practice than it is in theory.
The first step in teasing out ulterior motives is to do what therapists do every day, which is to consciously differentiate content from process. The question to ask yourself is, in addition to the information being transmitted, what is the underlying meaning of the encounter? What sort of global thoughts and emotions would this person probably want you to take away from the conversation?
There are any number of ways to hide an ulterior motive within the folds of content, but one of the most clever is to ostensibly make yourself look bad when what you are really trying to do is make yourself look good. People do this all the time, telling an embarrassing story about themselves where if you look hard enough you can see they are actually inserting details to make themselves come off as really cool. Seeing ulterior motives of all kinds becomes much easier if you can disregard the story for a second, realizing it is just a vehicle to transport what this person wants you to believe.
Much of this is unconscious and we all do it sometimes. We are not necessarily trying to be manipulative, we just have agendas, and being forthright about these agendas is not always socially sanctioned. You will feel much less confused about the actions of others when you think in terms of process instead of content, because their actions will usually sync up perfectly with their underlying motivations.