Knowing about a person is easy.
Bookstores are full of what others.
It is easy to know about God.
This principle also applies to knowing God.
However, if you really want to know the person, and not just gather facts about them, your best strategy is to talk directly to them and develop a relationship with them.
Just read all you can find about them and talk to someone who knows them and you can gather enough information to develop a good general idea of who they are.
Knowing about a person is easy