Learn to use 8 figure grid references by doing. A tutorial/guide sheet, a map, instructions and a list of grid references to find.
Attached sheets. Care needs to be taken to print the PDFs such that the grid squares (both on the map and on the tutorial sheet) are 10cm across- do a test print, measure, and adjust your print scaling if necessary. Scalings aren't necessarily the same for the two PDFs.
Give out the maps, tutorial sheets and instructions along with an orienteering compass with a mm scale. Done for cubs but probably useful for any that aren't too confident with grid refs. Less useful for those not in Lancaster for obvious reasons. :)