We've all been there, the party from hell. You just start
through Shadowfang Keep (SFK) and some n00b accidentally trains all the elite
mobs in the next two rooms right at your group! There is nothing more painful
than being stuck in a bad group. It can be especially painful if you are like
me and you devote time to your family and only run a couple instances per
A good leader makes all the difference in the world, in my opinion. A strong leader can teach players who don't know their class well enough. This happen to me during my first Wailing Cavern (WC) run as a rogue at level 15 - I had no clue had to use Sap at that point, I had never had a need for it at that point. The leader was kind enough to explain how I should use it and how we would handle the approach each time. He had the mage stand by to sheep in case I failed with the Sap.
I like to find a leader that knows the classes, someone who can handle n00bs that might not understand how to play their class well in a team setting. I also like for a leader who takes charge and explains his policy on healing, aggro control, and looting - I prefer things to be laid out before we start. I find the best way to tell if a leader will be good is by striking up a conversation about a bad instance experience and ask what their thoughts would be on avoiding that.
How do you guys determine if the party is going to be good, ahead of time? Or do you just let the cards fall as they may and hope you got lucky with your party pick? As you can see from the pic, my motto is: "When in doubt, dance!"