The 4:30PM Wednesday slot was packed at OSCON. I'm talking about three sessions I was either "eager" or "very eager" to attend at a conference where 95% of the conference titles were outright inscrutable. (eg. "Sun GlassFish (OpenSolaris) Web Stack – The Next Generation Open Web Infrastructure" — see what I mean?) One session concerned graphic design. Another risk models. The third session listed as "Antifeatures," a title which was tough to resist in its own right.
I told myself I'd pick one and sit through the first five minutes. If, at that point, it had met certain criteria, I'd bail on it for one of the other sessions.
If you are loathe to leave a session under any circumstances, consider yourself exempt from this writing prompt. Otherwise, if you value your time and you vote with your feet, how do you judge a session by its first five minutes? Again, it's possible the session turned into a winner exactly six minutes in. Under these constraints, though, we don't have the luxury of patience.
I'll post my own criteria to the comments shortly.