Plan a break to let your mind rest. Visual overload can be a creative killer.
Some of our smaller local shows have the vendors in the same building or even next to the quilt displays. It is easy to walk back to the vendors and purchase whatever you want. Normally, Pat and I look at the quilts first and then go shopping. (That way I don't need to carry bags around the displays - it can get crowded and they can get heavy).
If the show is large or the vendors are in a different building, my approach depends on time and money. I may make a pass through all the vendors to see what everyone has and then decide to go back and make my purchases. It's important to note the name and position of the vendor. If it's a special item or there is limited quantity - get it right away.
Careful not to get carried away. It's very easy to get caught up in the excitement of it all. Sounds like you have a plan and a shopping list.
Most importantly: HAVE FUN!!!!!!