Analytical Circles of Friendship

So...over the last few years I've been puzzled on and off by the very concept of friendship - what it means to be a good friend - and lately it seems this struggle has come to quite a head for me...

For instance, what is a "Best Friend"? How does one become someone's Best Friend? Is it a matter of knowing someone over time? Being a good listener? Able to make someone laugh? Availability? and how is it that people can have more than one Best Friend? Doesn't the very word Best in the title imply the inherent concept of 1 as opposed to many?
I've had very few people in my life I could call a Best Friend, none in recent years (unless you count my Mom), and as I think back on what made us close, the answers to these questions don't seem any clearer...

Even more my struggle as of late...what does it mean to be a Faithful friend? I feel this is my duty and joy, but I can't quite identify what a Faithful friend should look like...
Is this again a matter of a time requirement? You are considered a faithful friend if you stick it out over time? Or is it just about consistency, regardless of how long you have known someone?

And what happens when all you feel is drained by a friendship? When I became frustrated with a friend who shut down on me...I was certain it was time to abandon ship!!! What was the point?! For all the time, energy, and prayer I had invested, I felt I was getting little to no return on my investment. I wanted the ROI!!! Yet, I felt God clearly put me in my place! I was being selfish, He told me...I was called to be a Faithful friend regardless of what I got out of it...and when I accepted that, I felt great peace in the matter...followed by some wonderful, fun times with that friend...
Still, I don't think this is always the case...I haven't always felt such clear direction in this space with other relationships...How many of my friends over the years have drifted just far enough to be out of reach...and I felt it was the natural course of time and chapters of life...so when is it time to hold on and when is it time to let go?

Oh, and how much interaction does it take to ensure someone knows you are available to them when they need you without actually annoying them in the process?!? The last thing I want is to overwhelm anyone with too much Jenn!!! That's not a Faithful friend, that's just a mess!!!

So...I'll continue down this path of wonderment...and when I'm all done following the analytical circles in my mind, I may just still come back to the conclusion that I'll strive to be a Faithful friend...even if I don't really know what that SHOULD look like...