the weights first and then inflate the balloons. as you inflate each balloon tie it and attach the ribbon to the neck of the balloon (remember to leave enough ribbon at each end to curl later).
then measure the length you want the lowest balloon and tie the ribbon to the weight bag. don't cut the ribbon until you have tied it to the weight bag, otherwise by the time you have tied the knot your balloon will be lower than you'd wished.
repeat the process for the second and third balloons and finally use the back edge of your scissors to curl the ribbons at the neck of the balloons and 