I've been participating in VSN for years and each time I seem to add to my efficiency...first,start off with a clean work area. It makes it easier to keep things neat as you move along. If you're playing all weekend, straighten things up after the Friday event so when you come back Saturday, you've got a clean area once again.
Here are a few other tricks that I do:
1) I have a box of pre-colored images...sometimes I just feel like coloring so I color images and save them for when I feel more creative to make it into a card. Come VSN, all I have to do is go to my pre-colored images.
2) I have a basket with scraps, including folded card bases, that I always keep close by. I always check the basket first to see if there is something in there I can use for a particular challenge before slicing up more paper. Chances are I've also got coordinating DP scraps in the basket so it saves time from having to decide on patterns.
3) I have a binder that I keep printouts of card layouts/examples that I liked while scrolling through the gallery. If I'm stuck I can flip through the pages of the binder to get inspired.
Most of all, don't stress out, just have fun!