I don't really know what kind of diet to go for. I want to aim for 1000-1200 calories a day, and I usually start out okay but once it hits late afternoon and I'm at around 800 calories or so my energy levels kind of shut down and I end up grabbing random snacks that dont really help to keep it up.

This is espesially a problem on mondays for me. I go to university and monday I have classes from 8am-10pm with about a 4 and a half hour break scattered between. But as it turns out I end up having to wake up at 5am since I commute and by the time I get home it it well past 11pm. I usually wake up and rush to get a coffee and once at school I get another coffee and a bagel and go to my first set of classes. After that I tend to grab lunch (usually fast food) and then go try and do some readings for my classes. I have enough energy to concentrate until it hits 3pm. That's when my energy starts to crash and I get a headache and just feel really uncomfortable but I have no where to go.

So at this point I give up on trying to do work and listen to my ipod until about 30 minutes before my next class where I get another coffee. Then right after this class it becomes 5:30pm and my energy once again leaves.

At this point I tend to wander around aimless - which makes my body feel even more irratated and my energy level is just not around. Then I go to my last class at 7pm and barely pay attention to anything but my watch.

Once I get home I'm really exhausted and I just want to go sleep but I end up grabbing as much food as I can out of the fridge due to the caffine that is still in me and wont let me fall asleep.

So I end up going over what I want my diet calorie range to be on days like this.

Any tips on what to eat and time periods to eat it at in order to keep my energy up high? Also, several months ago I was told by a doctor to take Vitamin B12 pills since I tend to feel fatigued a lot, but I havent since I dont really see what they do. Would they help?

Your doctor was probably offering it as a placebo. If he/she really felt you needed b12, they wouldve been pushing b12 shots on you.

Unless you have a noted deficiency and diet corrections don't seem to help, you don't need vitamins or suppliments. Cases where you are demanding more of your body, such as intense training/weight training aside.

For a person just trying to lose weight, you want a balanced diet. You don't sound like you are eating enough. What is your height and weight?

Also are you getting enough sleep?