You need to realize that to reach your goals and STAY there, you need to change your life completely. You can't just say "hey I want a 6 pack, lets work out untill I get one." You don't have to go on a crazy diet, just be aware of what you are eating. You don't have to go workout crazy (you will if you want a 6 pack) just make a habbit of 45-60min a day, 5 days a week and you will probably get into pretty good shape and stay there. But then most of all, you will need to increase your daily activity.
To accomplish a decent level of fitness, you need to get off your ass as much as possible. Just do something other than sitting. Do some yardwork, work on the car, fix some things around the house etc. People don't realize how beneficial it is to not be a vegetable all day long.