Im no expert but I try to follow the "Biggest Loser" rules and tips etc. After all, they should know what they´re doing!
If you don´t want to buy any of the books (which I highly recommend though) you can take a look at this page for some guidelines:
'The Biggest Loser' Diet
If you want to lose weight in a more normal way so to speak you should eat around 2280 kcal a day. If you want to lose weight biggest loser style you should eat about 1950 kcal a day (and also exercise 4-6 hours a day!!!