PLEASE HELP!!! DIET!!!?

i have always been very concerned about my diet, but since my family will be going to aruba in the summer, I need to lose some weight. I am 5'7 almost 5'8 and I am 127 lbs. I would like to be 120 or even 115 by the time I go to aruba. Any suggestions on how to do this? PLEASE, i need help!!!!!!