How many calories am I supposed to eat to lose weight?

This is something I have confused myself about. I am very much into the idea of eating healthy and intend to do so, (I've recently decided to try a Vegan diet based on personal beliefs about animal rights, the meat industry being destructive to our environment and because I've read plenty of literature suggesting that meat is not good for people. I need to lose weight about 25 pounds and have failed time and time again because of my food addiction and not sticking with a exercise regime but too, I always confuse myself when it comes to the calories. I can survive off of 1200 calories without feeling deprived but I've heard of starvation mode and metabolism. I've heard that that is the amount to eat for ultimate weight loss combined with exercise and then I heard that by eating that amount and exercising you body would go into starvation mode and not give up the fat. Please help me figure this out. I don't want to eat more then I have to so could you tell me what I am supposed to be eating. Thank you.