First, if you're overweight, you must identify your weakness and put it behind you, forever. In my case, it was snacking after dinner. Not only did I have to stop, I had to accept that I could never, ever snack after dinner again--no exceptions. Lots of people lose weight, but very few can keep it off. You can never go back to whatever caused you to gain.
Second, you must make exercise your top priority, each and every day. You can only go so far with weight loss before your metabolism resets itself, and you hit a dead end. Exercising for as little as 30 minutes a day will keep the calories burning. No exceptions--daily! You'll have to be come a bit asocial--someone invites you out to a lunch that conflicts with your exercise period, say no to lunch.