Examine

Examine men’s ruling principles, even those of the wise, what kind of things they avoid, and what kind they pursue. – Marcus Aurelius

What does that mean?
I think, this is about choosing friends and acquaintances. Are they the kind of people you want to be around?

What are the values and principles which guide them? In some particular situation, how will they respond and what will they do?

The implied question in the quote is “are they right for you?” Will they be the kind of person with whom you want to be associated? Will they give you the help and advice you need, or are their goals different from yours?