There are no quick fixes. Get off your ars* an put the effort in.
Just adopt a healthy lifestyle.Eat a good healthy diet and excercise a lot!!! The more excercise you do the better!
For a healthy diet, you need to be eating small to medium meals regularly. 4 or even 5 times a day. Each meal (apart from breakfast which should preferably be fibre rich), should contain a balanced ammount of carbohydrates for energy, (from potatoes, rice and pasta, etc) protien (from fish, chicken, occassional red meat is fine, soya is good too) and plenty of vitamins, minerals and antioxidants (simple fresh fruit and veg). Eat like this and make sure you are well hydrated (fruit juice is as good as water, any fluid counts, but some fluids have negative effects too, such as alcohol or caffiene rich drinks.)
You can have a wide range of healthy meals with this, from Thai, Chinese, Italian, British, Indian, etc. Just make sure each meal contains balanced ammounts of these three. On the bright side too, fresh veg and rice and pasta is a lot cheaper than crappy junk food!
This doesn't mean you cant have chocolate or pizza/takeaway/etc, just save them as very occassional treats.
The big secret to keeping a healthy weight and staying healthy is EXCERCISE, particularly cardio excercise.
Cardio exercise includes any form of excercise such as running/jogging/swimming/cycling etc that gets your heart rate pumping and you sweating and out of breath. It will not only burn calories and reduce your body fat levels, therefore making you 'slimmer' by having less fat on you, but will also improve your resting heart rate and lung function, making you healthier.
I cannot understate the importance of cardio excercise. It is this which will basically burn the body fat off you.
But you have to remember that once you have shed a bit of fat you have to have a nice toned body underneath the fat to show off.
Strength training will help you strengthen and tone your muscles. This is done with the use of weights or by free training.
There are essentially (without getting overly complicated) two types of strength excercises based on different types of muscle fibres depending on wether you want to build size, bulk and power, or just 'tone' up the lean muscles an get more muscle endurance.
Heavy weights with short reps/sets will build your fast twitch muscle fibres and build size, power and strength. Imagine big guys at the gym lifting heavy weights.
But if you use light to medium weights with lots of reps/sets you will excercise your slow twitch muscle fibres, you wont build size, but you will tone up your body and train muscle endurance. This will obviously make you 'look' healthier and more toned, but will also increase your metabolism (as your muscles demand more energy) so you will burn calories faster. These muscles are also excercised a lot with cardio workouts (i.e your leg muscles when running).
Your arms for example, will need bicep curls and tricep dips using weights and reps of your choice (heavy - low reps, light - lots of reps) and also shoulder excercises such as holding the weights at your waist and lifting them perpendicular to your side or in front of you, etc etc.
Your stomach will need excercises that cover the entire torso. Leg raises for your lower ab wall, crunches, sit ups and planks for your upper and all over ab wall, oblique twists for your sides and superman stretches for your lower back for example.
These are just basic examples, there are literally hundreds of excercises, but it is impossible to show you on a site like this, get a trainer at your gym to show you some but remember the basic rules of muscles and weights.
As far as excercise goes, you should aim to strike a balance between cardio training and strength training, this way you will build good strong and toned muscle, but also keep your body fat levels down and increase your heart and lung performance, making you much fitter and healthier.
Hope this helps.
Nurse and ex army