I wouldn't recommend going on a crash diet, you need to aim at a very slow but constant weight loss, if you can do that maintaining a more healthy weight will be a lot easier.

Avoid refined foods and concentrated on food that is as natural as possible cutting down on carbohydrate and fat.

Eat slowly and make sure you know how much carbohydrate, fat etc you are eating then you can gradually cut down until your weight begins to decrease.

There is some handy info here.

http://healthyeating.sfgate.com/lose-weight-simply-eating-less-2777.html