As a college student, I've been off and on more training programs (...and then came exams) than I can count. The one for beginners that I see over and over again, however (and that always works for getting me back in shape...before exams) is as follows:
* Get in around 15-30 mins of cardio a day. Jog, walk, use a stepper, bike, whatever. Just do it.
* More veggies, less sweets, less fast food. That's just common sense.
* Since you have a membership to the gym, the best starting weightlifting routine that I've found revolves around a four day program, 3 days 'on' and one day 'off.' If you're going every other day, however, I can see the following situation:
Monday: Chest, Back, Calves, Abs, Cardio
Wednesday: Shoulders, Biceps, Triceps, Abs, Cardio
Friday: Quadriceps, Hamstrings, Calves, Abs, Cardio
Saturday: Lots of Cardio, Abs
For each muscle group, I'd start out with two exercises (Bench Press and Dumbell flyes for chest, for example), and do two sets of 12 to 15 reps each. At first, don't worry about doing big weights; just aclimate your muscles to the motions and get them used to balancing the weights. As you get more comfortable with the motions and a bit stronger, you can increase the intensity/weight. After a month or so, experiment. Try adding another exercise to each muscle group, another set to each exercise, doing less reps at more weight, etc.
Let us know how it turns out for you!