The everything else line feeds into the convention center around like 7 am (someone else can give the proper time if it's that important). From there, there are usually 2 lines to get into the exhibit hall; one by Sails and one by Hall G. Those lines open are both let in at 9:00 am. The sails line feeds into the middle of the hall (around the 2000 booth numbers) and the other line feeds into Artist's Alley.
If you want to just walk in, those doors usually open around 9:30 but it's much more dependent on how much of a power trip the security guy watching that particular door has. I've definitely been stuck outside at 9:45 because of this.
If you absolutely have to be in the hall at 9:30, you'll want to be in the everything else line before 9:00.