Need to lose significant amount of weight by early December

juicyfruits72

My year 12 formal is coming up and I had a beautiful dress picked out. Now, a few months later, I decided to try it on again and it's too big! That was my motivation to lose weight again. Has anybody tried to lose 6-8 kilos in three and a half months? If so, what workouts have you done/what have you eaten? What has kept you motivated? How many calories do you eat per day. Thanks in advance