Generic advise here, but this is working for me.
I think the thing which really hit me and probably is true is to not think of it as an attempt to loose weight, but as lifestyle change. I saw that on these forums, and it is probably true. I started with fairly small steps, such as drinking a bottle of water a day and going for a small walk. Accepting you are not happy with yourself is the best motivation I think, and after two years of ignoring advice from family and friends, I began to make a change.
Three months on from these steps I have a fairly routine meal plan, do approximately 70 minutes of exercise throughout a day and don't really snack that much. The way to do it is to slowly add more parts on to what you do. For me in the last week I added a 10 minute jog (Wii fit) on to my daily exercise. I've currently lost about 35 pounds since I started this with an aim for 42 Pounds/3 Stone total.
Also try to cut down on the smoking if possible, saves money and extends your life.