Everyone here seems to say it's diet 1st and exercise as a distant second, but in my case I'm not sure that's true. I don't really get worried about what I eat and I certainly don't count calories, but I've lost 49 lbs since February. Oh I did make some adjustments in a sort of general way. If I eat a heavy lunch then I take it easy at suppertime. I've always preferred diet drinks so that was no problem. I try to be aware of how much snacking I do and take that into consideration when I'm planning my "real" meals. I don't shy away from fried foods or desserts, but I always remember what I eat and keep a general idea about how much more I should allow myself to eat in a given day.
Mostly though, I run. I have not missed a single day of exercise in the ~180 days since I started. I got caught in the rain twice while running in that time, but I really didn't care that much. It's gotten to the point where running seems as necessary as brushing my teeth in the morning and showering at night. The second month in I added some free weight training five days a week. I use the simplest routine imaginable (of my own devising) for strength training, but I've had fantastic results. I imagine that if I didn't have some muscle gain to offset my fat loss my weight loss numbers would be more in the 60-65 lb range.
So the secret (IMO) is simply to remember what you eat and cling to your exercise program (whatever that may be) for dear life. I like to run personally, but whatever it is you like to do, do it every day. Forget hard days at work and social engagements and whatever other excuses there are that might stand in your way. When the workouts start to get easy bump up the intensity in whatever way you deem appropriate, but don't let them stagnate. Remember that steady progress toward your goal is what's going to keep you exercising.
