I was a part of the organising committee last year, and was also there all day from set-up to pack-up.
My personal thoughts on the whole day were:
* This year, to make it a success you really need to promote it!
Last year we tried to use the AkCC public noticeboards, but they were booked out months in advance - so no go. Some flyers were put up around various places, but from memory they were just plain B&W photocopies - so not 'noticable' at all. We managed to secure a deal with a Radio Station to talk about cloth nappies over RNW, and do a BIG giveaway, but I don't think they really plugged the event (however this was a freebie, organised by an employee who no longer works there unfortunately

)
You need to come up with innovative ways to get the word out there. The event itself can be fabulous, but if no-one turns up, then it will be a flop. This is the one area where I think the most work needs to be put in.
*You need a bigger venue than the place last year
On reflection I remember looking in the room at the GLCC last year and thinking how intimidating it looked! It was a small room jam-packed with tables all set up in a semi-circle looking at the door. So when you first walked in all you could see was a nappy demo table in front of you, with 6 or so tables surrounding the demo table with nappy retailers eyeing you up

Ok, so it wasn't that bad, but you get the picture?
*You need more people for pack-up/cleaning than you do for set-up
We had too many people there for setup imo, and not nearly enough for packup. Pack-up is always going to be difficult as it will inevitably co-incide with dinner (even bed time for some kiddies), so people will not want to help out with this, but rather be at home (and fair enough!)
The other thing was as Nova said, I don't think we had any visitors after 3pm? Perhaps one or two? You would be better off having it from 9-3 instead of 11-5 or thereabouts.
*Make sure the people you have helping out are passioante about cloth, experienced in the different types, not affiliated to one specific retailer, and have enough cahoolies to chat to visitors
I struggled in the cahoolies department, and felt emotionally drained at the end of the day

(was on the nappy demo table for most of the day)
*Would be cool if there was food for the helpers there (even if it was just a bunch of grapes, packet of chips, or heaven forbid - chocolate biscuits) and drink.
Perhaps even just a reminder to your helpers to bring food/drink with them on the day. I was so busy that I forgot to bring stuff, and was ravenous and thirsty(and being 4months pregnant didn't help!).
Hmmm, lots more to add, but mind is blank. Perhaps one of the others from last year can add something???