IMHO, if you aren't working up a good sweat you aren't working hard enough, plus you don't need to spend hours on a cardio machine to work up a good sweat. Try going for quality rather than quantity, you'll spend less time in the gym and maybe, just maybe more time on studying
Stick to one machine rather than jumping from one to the other. Do some HIIT instead, here is a
site which explains it.
There are several sites and books on weight training... It just depends what you want. If you go to the gym 4x/week, maybe workout the upper and lower body... if you go 3x/week, do a full body workout with a day of rest in between.
Here are a couple of sites for workouts:
http://exercise.about.com/od/totalbo...y_Workouts.htm
http://www.stumptuous.com/ -- This is a really informative site and funny too...
The most recent book I'm reading is New Rules of lifting for women...
So the sky is the limit, use your imagination and go for it... What works? Is whatever you do consistently and continuously, that's what works
... Your food intake has to be good too, 80% of weight loss is in what you eat... So eat healthy and put the junk food aside...
Hope this helps keep us posted on your progress...