to add a bit to what Aph and Sark has said.
when leading also don't expect to have everyone happy with you and do expect to have to have to tell people leave the raid, or tell people they can't go due to gear reasons (becomes a bigger problem when you get up to the top content)
another note from past experience, just because people sign up to your raids or say on the forums they want to come, it doesn't mean they will. this is the reason I stopped doing Super as people were quick enough to say they want it and to sign up but when it came to doing it no body cared. (I was actually using pretty much entirely alts due to this)