i used to weigh 80kgs a year and a half ago with around 21% body fat.. im now down to a VERY lean 74kg with 9% body fat. these are the rules i've been following:
1) do heavy weight training 3 times a week. keep lifting until you want to die. its been proven that lifting weights burns a lot more fat and calories than cardio.
2) do about 30 mins of cardio every day that you dont gym. this keeps your heart healthy, your metabolism super high and also has the added affect of accomplishment (wow... i just ran xKM in y Minutes... thats not bad... I ROCK!) (i love running, you may prefer cycling or swimming etc)
3) eat 5-6 small meals a day. plan your meals. if you get up at 6am and go to bed at 10pm, make sure that you dont take in a lot of carbs after 3-4pm. if you're gymming, take a protein shake before bed (it'll help your muscles grow and recover quicker)
4) fruit and veggies. i have an apple with breakfast, an apple with my 10 o'clock snack (protein shake and low fat yoghurt), a serving of steamed mixed veg with lunch (around 150g) and again with supper (also around 150g)
5) eat breakfast. a healthy breakfast with lots of fibre and protein. your body has been starved for 8 hours (if you sleep 8 hours a night like you should...) i mix some pro-nutro with high fibre bran for my cereal (don't know if you have those where you stay) basically, its a mixture of high GI and low GI with a high fibre content. perfect breakfast combo.
6) cut out fizzy drinks. i ate healthy crap and cut out fizzy drinks. i didnt even have coke with my brandy, instead i switched to whiskey and water and eventually to neat whiskey (chivas reagal FTW!). i've always gotten hammered 3 nights a week... in fact, i cant think of a week this year where i've not been drunk at least 3 times. the only change i made is in what i decided to drink. dont drink beer. dont drink anything that's mixed with a carbonated drink (except for gin and tonic...) have whiskey and water. have vodka on ice. lighter spirits tend to be less fattening, dont take that as a rule though. make sure to drink at least 1.5L of water a day... if you dont feel like changing your alcohol or anything, just make sure you drink at least 1.5L of water. i cannot stress that point enough. your liver needs that water!
7) take a multivitamin every morning. yes, i know, a lot of people say its just and ingredient for expensive urine. thats BS. a good multivitamin has minerals and vitamins in it that you wouldn't normally get in a normal diet, which is why it is crucial to take them. another point to consider is that you may not be getting the recommended amount of minerals and vitamins in your body each day. although the excess can easily be gotten rid of (expensive urine), a lack thereof would put your health at risk. take a multivitamin. especially if you gym and lift a lot of weights.

tan. yes, i know, this is kind of contradicting because in time you'll be leathery etc. the fact is that a person is less insercure when he i tanned than when he is pasty. if you feel that lying around and tanning is gay, start swimming. i've always been exceptionally pasty and decided to start tanning after my ex left me. i've never looked/felt better. no jokes. remember sunscreen though... peeling is gross and skin cancer is kinda deadly, so lets try to avoid it!
thats my advice. i used to be extremely insecure but every day i get more and more confident. im in better shape than i could've ever imagined and that gives me even more of a confidence boost.
everyone can have a killer body, it just takes more work for those who were placed on the backseat by our genes. fuck our genes. i didnt allow my genes to make me feel insecure anymore and neither should anyone else. insecurity is for those who are either too lazy/scared to try make a change or for the exceptionally ignorant. pickup isnt just about learning how to get ass, its also about improving your social skills... and confidence plays a big part in that.
make the change. it'll be hard and tedious but you'll thank yourself with every day that goes by.