Every relationship in life is so different from the next, how do you ever know if someone is really worth it?

I have some friends who really get who I am.
I have some friends who really get who I am, but I don't neccesarily get who they are.
I have some friends who act like one person, but become something else when they are under stress or pressure.

I have some friends who haven't changed since I met them.
I have some friends who have changed every month since I met them.

I have some friends who speak my language perfectly.
I have some friends who can read my body language and facial expressions.
Most cannot though.

I have long distance friends who can calm me down quicker than someone standing next to me.
I have short distance friends who can cheer me up quicker than chocolate can.
I have some friends who give me chocolate.

I have friends who are down a lot.
I have friends who I've never seen cry.

I have friends who paint, friends who enjoy cigarettes and coffee, and friends who like to take long walks.

Which one should I trust?