I've lost weight and gained it many times as a result of being a retired serious athlete.
The biggest thing I've found if you really want to lose weight is that you must change your habits and how you live. You must change your lifestyle. If you don't, you'll just put the weight right back on as soon as you end your diet. However, if you've changed how you live you are no longer on a 'diet'. You are just eating like normal, in your new style of living.
If you sit around alot, get up. Do something, anything. Just change the habit. Also, starting to cook for oneself is a great benefit and step. It takes time, but don't treat it like a chore, its an event. It can be fun. And it absolutely is enjoyable.
Watch some Gordon Ramsay, he will inspire you to get into cooking great food for yourself. Plus, when you cook for yourself you know exactly what you are eating. Portion control is back in your own hands, and it only gets better from there.