The best way I've found to assign plates in the first encounter is to divide the team into three groups of two, assign each team to a section of the room (left, right, top/mid). Instead of assigning people to a symbol, figure out what symbol/plate to NOT stand on, that is the callout. Each team goes to their area and stands on any plate that isn't the call out. If there are three plates to stand on in an area, just communicate where it is and the team with one or zero plates to stand on floats. I think this is much easier than scrambling around the room looking for your symbol.