I've seen it posted many times as I was scrolling through, but definitely a lifestyle change vs. a quick "off and on" diet will help you. I used to weight about 250lbs at 6' tall before I joined the Marines, I can honestly say, its mostly about the diet.
Eat clean - meaning lean meats, and the right portions.
It may sound strange, but eat often.
Small portions will keep you feeling "satisfied" not full, throughout the day.
Exercise will help immensely! Not sure of your situation, but I'll get up in the morning and complete a 3-5 mile run about 5 days a week, then hit some high intensity training in my garage, or the gym if I'm near work.
Find out what your resting heart rate is and what your max heart rate is. As long as your hitting close to your max, you'll be losing fat. the active.com site has a good calculator: http://www.active.com/fitness/calculators/heartrate
Remember, when it comes to exercise, a lot of the weight lost at first will be water weight, this is the type that comes off easy, but comes back just as easy.
Finally, (and I have my wife to thank for this) I'll juice about 2-3 days every other week, all you do is strictly drink freshly juiced vegetable juices during those days and it will cleanse you out! Works too, I've been known to drop about 10 lbs in 3 days with the juices I make. But don't rely on this to permanently lose the weight, just use it as a cleanse.
Finally, just keep at it man, if you need some motivation or just want to talk about the lifestyle change, Message me!