I think I've attended enough conferences (and thus conference sessions/workshops) to identify the characteristics of a worthwhile session for me.
First, I would say a good conference session is grounded in theory. I want to know why what is being proposed works. I want it to connect with relevant research - that can be research done by traditional academics or research done by teachers in their classroom.
Second, a good session gives me ideas for structures, routines, and sequences that I can use in my classroom with my curriculum. Too many sessions that I've attended have been just teachers giving me their very specific assignments or activities. I don't need more activities - I have a gabillion of my own that I don't have time to use. I want to be enlightened about how I could structure things differently or ideas for structures in the classroom that will fit into any curriculum. Or, in the minimum, be given multiple ways to accomplish an objective so that I can pick which works best for me. For instance, in the aforementioned session with Kylene Beers, she demonstrated different ways to teach vocabulary. I can use those in my classroom without changing my curriculum. A few sessions I went to talked about commenting on student work or conferencing with students. Again, this works in a multitude of classrooms with any curriculum. But, I also attended a session where I was given the exact assignment that someone gives their kids, we did the assignment (a sped up version), and that was it. It was a nice assignment, but it wouldn't fit into my curriculum.
Thirdly, the opposite - all theory. I love theory. I really do. But, as a working teacher, I need to at least see how this theory could work in the classroom. I'm not saying that I can't apply theory in my own classroom, but I want to see how it worked in the presenter's classroom. I want to a session a few conferences ago where the presenter just put quotes from famous educators on the transparency machine and talked about them.
Which leads me to my fourth point ... I find it difficult to believe that teachers can be such horrible presenters. I'm not saying that I'm the best presenter in the world. I'm certainly not. But, I have trouble believing that career educators are reading PowerPoint slides to their audiences.
Finally, a good session is what was described in the program. I went to a couple sessions that I had no idea how what we did in the session related to the title of the session or the description. That is a waste of my time.
Most of the sessions I attended at NCTE were magnificant - given by inspired teachers who must elicit immense amounts of success from their students. I recommend anyone to go to an NCTE conference.