I don't know if I'm the best leader. Never really had any PUGs compliment my leadership, then again I'm fairly certain that people know what they're supposed to do when I lead as I say it about as straight forward as possible. Haven't really had any super big issues, but yeah. I usually try to do guildies first and then if we can short it, do it that way. I'm very guilty of keeping to my own little group, but then again I hate failing stuff. Unless there's a large majority of a raid (33%+) that don't know it, I usually expect some completion unless the Lag Monster strikes.
The one thing that usually prevents me from joining PUGs is group expectations. "True Rogue/Cleric/Wizard/Tank/etc needed" and yet there's a splash class with just as good of stats and everything, but they don't get to join. But hey that's the group leader's expectation/wish although some need to learn that splashes can sometimes offer more than pures