I started out at 250 - that was the magic number that made me realize I had to do something! I'm only trying to get to 160 - the number my doctor said would be my healthy weight. I've made it down to 172. I started the whole thing last July, so it's taken just over a year so far. My advice would be to go for 10 lbs at a time. Each 10 lb loss has been a real celebration for me. Also, you'll be amazed how much better you look and feel even losing 10 lbs and it just gets better and better as you go along.
Find healthy food that you love and write everything you eat down on the food tracker. I look at it several times a day to make sure I'm getting the right amount of nutrients and calories. Don't starve yourself and don't deny yourself - just don't eat a lot of empty calories.
You can do this!