What is the best diet and exercise regimen you've used to lose 30+ lbs in four months?

I want to lose weight for a trip over spring break, which is in the end of March/beginning of April, but also for my health and my own self-image in the long run (especially since college will be here next year as well). It's Nov. 28th now, and I'm starting my diet today. So far I have cereal for breakfast (low cal) and for my lunches I bought protein bars because I never have time to pack my own and I end up eating badly. I'll figure out dinner, which will most likely be a salad throughout this whole thing. What can I do on a busy schedule where I wake up at 6:15 for school as it is, and because of work right after, don't get home until 10? I need to lose roughly 10 lbs a month, and I am 5'4, 226 lbs, and 18 years old.