I highly recommend you set up a demo table before any convention where you have a new setup (I do demo tables before EVERY con, it helps me pack and allows me to organize my thoughts and get my head in the game), but what do you do when you DON'T have a folding table to use?
You make your own!
All you need for this tutorial are your convention setup supplies, some masking tape, and a ruler.
I measure a 2' length on the floor (preferably wood or tile, but masking tape will work on carpet), and apply my tape along the ruler. I then measure a 6' length on each side, perpendicular to my 2' tape, and mark the 6' length off with a piece of tape. I then run my tape role from the 2' tape to the mark 6' away, and from that 6' end, I mark off another 2' length. Finally I connect the other 6' length, making a 6'x2' rectangle on the floor.
From here you can begin arranging your setup. I find that using my tablecloth on the floor not only makes it dirty, but makes it difficult to balance my wire grids, so I skip the tablecloth and just begin building my grids.
When I'm not flying my setup, I like to use a curtain rod to hold my banner, as it's lightweight and fairly sturdy. You can secure your cheap curtain rod with zipties at the show.
Since I hat a lot to display, I wanted to make sure it would all fit, so I did a more fleshed out setup than normal, placing my mini watercolors.
Once you've determined where everything is going, take photos for reference during con setup, and take inventory to make sure you're not missing anything. This is a great opportunity to run to the store if you're missing something- better to find out at home than at the show. Once I know I have everything I need, I can start carefully breaking everything down and packing it in my large rolling suitcase for the show.