Loseit.com (or some other diet monitoring source.)
The number one thing someone can do to succeed is be aware of what they're consuming - use a website, app, excel sheet, notepad, whatever. It is eyeopening what we're really consuming (I'll bet that KitKat is 250 calories, which is over 10% of an average persons' daily intake needs. That said, I had a Nutrageous candy bar last week and loved it, and don't regret it.)
The number two thing is don't bar yourself from occasional enjoyment of the things you enjoy - just make room for them, and eat them less often. I still eat pizza, chocolate, and drink beer - life wouldn't be life without them.
Eating out is scary - I used to eat out a lot too, and still do sometimes, but I'm making slightly better choices (Mongolian grill instead of tons of fried stuff, for example).
Set multiple reasonable goals - my original goal was 30 pounds lost, and it probably should have been a little less. That lets you have multiple opportunities to succeed.
Treadmills are tough, but better with something to take your mind off. Set a goal/target with that as well - if you're not a runner, maybe try the Couch to 5k Program (C25K) - it will give you a way to work on, and make, incremental progress. It works on treadmill or outside/on a track. I went from running nothing, to running a 5k, in just a few months.
It's really simple, but challenging - consume less (but still the right amount for your body), consume more of the right stuff, and be active more - which can be anywhere from walking the stairs at work/school, to running marathons - where ever your body and fitness level is.
Find a support system - here, the websites for the tools (again, I like Loseit.com), local people, Meetup group, etc.
The motivation does have to come from inside - until you realize "I want to do this", all the people telling you "You need to do this" won't make a difference. But having a support system can help that motivation going.
Realize you can do it, and don't let small stumbles mean failure to you - it's a long term habit change, quick-loss doesn't work.
And be proud of yourself for making the decision and taking the first steps
