When I am preparing for a crop I gather the photos that I want to work on. I then start putting together page kits in 2 gal. ziplock bags. I gather the cardstock, patterned paper, and embellishments I want to use. I put all of that with the photos into the bag and I try to get about 2 bags ready per hour just in case my creative juices really start flowing at the crop. In my opinion it is better to bring to many layouts than to run out of pictures to scrap.
This would be a great way to use some spare time at home as well so when you do get those precious hours to scrap you are ready to go.