I usually end up as the coordinator. I don't call it 'Leader', because I really don't give orders so much as suggestions. The way it goes down is usually like this:
Rd. 1 - complete clusterfuck
Rd. 2 - complete clusterfuck
Rd. 3 - I finally say "Okay... look... we've got to get organized here. Seriously: player A, you seem to like to do , so . Player B, you're obviously a so ; and you should probably do , Player C. You're obviously really good at it... I'll clean up the rest"
Rd. 4 - I say " remember my suggestions last time? Let's try it this time, okay? Seriously, if it doesn't work, I won't say shit ever again."
Usually, Rd. 4 is when we start rolling. After that, it's all good. Generally speaking, when you at least define what people should do, they're much happier and efficient. There are- of course- exceptions to the rule, where it is going to be a rolling ball of fail regardless of how much you try to help people.