When I was in my first year of college I was faced with the same dilema. I had taken a class called Physical Development or something and it was basically weight training and exercise for 1 credit. So where to begin? I could not bench or squat with the machines being occupied by football players and the like. So I started out with some cardio.
I got on the Stairmaster my first day and did a routine called “Blast Off”. I paid dearly the next day of course, haha! After that I just developed a circuit training type workout. Here is a general idea:
Cardio and Stretching - Brisk walk for 60 min, stationary cycle, stairmaster.
(important to stretch and loosen up a bit before). Did abdominal work mostly, along with free weight curls, pull ups, push ups, lunges with dumbells, etc.
Upper Body - tricep pushdown, seated rows, Preacher curls, lat pulldown, bench press etc. (include some crunches, flutter kicks somewhere for mid section)
Lower Body - leg extension, calf raises, leg press, leg curl, hip adductor/abductor (include some crunches, flutter kicks somewhere for mid section)
One thing that helped me out a lot was finding a friend in the gym. Someone to spot you and talk with during the time from one machine to the next. It provided me with motivation and a sense of competition as well (I wanted to outdo my gym friends).
Don’t be afraid to ask for help either, if you see something you would like to try and you see someone else doing it, dont be afraid. It’s the only way you will learn.