Early on I fell prey to the mentality that once you put a round into an enemy, he was "yours". After a couple of instances when I wound up taking hits from the claimed target I started to think more selfeshly.
I will tend to avoid conga lines as they are likely to cause killshots with all the traffic. when I come across a 1 v 1, I try to get a handle on whether the friendly is ok or struggling. Many times there is no reply to my query, it does get busy.
My tactic is to fly as a sort of "big brother" if there's a need, I engage.
I have lost count of the augers caused by my trying to avoid cutting someone off but even that diminishes with time.
All that said, I still get the occasional shot from a friendly that I did something innappropriate. I never apologise.
As far as having kills stolen, if it happens twice, I do whatever I can to insure that pilot gets nothing but assists till he changes sides.