What are the qualities to keep in mind while associating with people?
There are lots of qualities of people to keep in mind as you associate with them. Based on the attached text, though, one quality to definitely keep in mind is whether or not the person that you are associating with is a "self-seeking friend." In fact, the attached text goes so far as to say that you should "shun" those people. The writer says that you should shun self-seeking friends in order to "conserve your resources."
I don't necessarily agree with every single part of the attached text, but I do agree that it is wise to be aware of which people/friends are self-seeking. My own students would call this kind of person a "user." Not a drug user. This is the kind of person who never has money on them, so they are constantly borrowing from friends in order to buy lunch (or whatever). Their gas tank is always empty, so they always need a ride. This type of person puts his/her own needs first (which makes them self-seeking), but expects other people to help provide for those needs. The author of the attached text warns against that kind of friendship because it is a very lopsided friendship. One friend is always doing the giving, and the other friend is always doing the taking. It's exhausting to always be giving and never have the friend "return the favor." And like the text says, it does put a drain on personal resources, if the friend is never repaying the favor/loan/goodwill.