It`s is quite simple.
The latest list will be displayed whi are presently online and accordingly it will display the list of friends.
The last login being shown first in your friends list and so on.
Or is there any way to find out who check their facebook profile,
which checks his friends` profiles?
It`s possible when we add them as our friends.
Your name will be displayed in visitors list.
This is helping a person to know who has viewed his profile.
The other way is find through use of proper tracking software which will help you.
The better option doesn`t expose your private life in public otherwise it will not be private anymore.