2.) Start cooking. Eating out in London is expensive, no matter how "cheap" the place is or whether they have a student discount. I've been going to Sainsbury's and Waitrose to buy groceries, but I know I really should check out local markets for better deals. So far the vegetable and produce at Waitrose seems like better quality than other places, so it may be worth it to shell out a few more pounds for food that lasts longer.
3.) Buy an oyster card even if you are a tourist. My Dad was spending 4 pounds a trip when he was taking the tube but if you buy an oyster for 5 pounds the rides become 1.90 each way. My friends have signed up for the student cards for even cheaper fares.
4.) School pubs have worked out pretty nicely so far because they have cheap drinks. The University of London Union Bar has beer and mixed drinks for about 1.50 each. Not bad at all!
Pre-gaming or as they say here, "pre-drinking" at home is also a good idea. I love Stella's apple cider. It's really yummy! You can also pick up a liter of Tesco's apple cider for less than 2 quid.
5.) Do not buy American makeup products. Brands like L'Oreal are more expensive in pounds, so a lipstick goes for about 8 pounds (about $12). Instead, I would suggest buying from Boots brand, Rimmel, and other local brands.
6.) For cheap apartments to stay at, check out airbnb.com.