Oh and forgot something else, a friendship has to be a two way thing, both parties interested in the other person- meaning they are just as interested in you and how you are and not just interested in themselves and what affects them.
This may sound a wee harsh but fairly recently I found someone who I would have thought of as a long time friend , well let's just say it was more a one sided thing.
They are not Christian so I shouldn't be that surprised really I guess??? ( non Christians can of course still be good friends but if they don't share your faith it is not the same)