The most important thing is motivation. You can't just willpower your way through it. You just can't. Instead you have to create motivation. You have to create habits and passive curbs on your behavior that make it so that even if you do everything else wrong you at least don't make it worse, and so that it's easier to do the things that help. Again, forgive me if this seems patronizingly obvious but I see so many people try so hard to stick to something unsustainable rather than changing their habits forever.
Here's the list of things I did that worked:
1. Eat a salad every day. Every single day. This is probably the easiest since you're actually adding food, but tricking your body into eating better food by slipping a proportion of fresh veggies into the mix.
2. Make fresh fruit more easily obtainable than other snacks. Personally I like oranges, so I try to make sure there's a bowl right in the kitchen with 3 or 4 of them. I also always keep some raisins around for when I am out of fresh fruit. I try not to keep chocolate or ice cream in the house at all. Create a habit of snacking on the good stuff.
3. Don't eat after 9pm. At all. Ever. Watch Gremlins, watch what happens when you feed them after midnight :) Seriously, from all that I've read it seems your body takes late night food and converts it into fat all night long, which has the unfortunate side effect of also messing up your sleep cycle. If you don't get to bed around midnight pick a time 3 hours before bedtime, but stick to it even when you need/plan to stay up later. I'm not perfect about this but it's gotten to the point where if I'm looking for a snack at night, I look at the clock and at least second guess myself. They say if you do something for 3 weeks straight it becomes a habit, and I've found that to be true in this case.
4. Skip a snack and feel good about yourself. Don't take reduced portions and don't make up for it later- just take a time when you wanted food but didn't eat it and tell yourself what a moral giant you are.
5. Exercise 30 minutes every other day at minimum, and at least once a week in the winter when it's super inconvenient (as it usually is). I have found that there is no solo exercise in the world that can compete with jogging, and for me doing it on a treadmill isn't the same as doing it outside. sonbanon and I have actually talked about moving to a warmer climate for this sole reason, so that it will be easier to get convenient exercise all year and hopefully I won't need bypass surgery in my 50's like my dad did.
The last thing, and I'm afraid I might not be able to help you with this one, is that you should have a lovely spouse who will replace some of your habitual evening restaurant meals with healthy and interesting home-cooked ones that have not been test-marketed to the customer base of TGIFriday's. If you don't have a lovely spouse to help you out with this then you may have to make other arrangements or even begin cooking yourself.
I won't wish you good luck because luck ain't got no say.