Hi Kwtr,
The best way to lose weight is simply to stay motivated and disapplined at whatever method of weight loss you choose. Keeping a healthy diet and staying away from too many carbs and calories in a day can be your most beneficial change. Lots of cardio (keeping a high heart rate) and some weight training (as muscle burns fat the most efficiently) will give you the fastest results.
Staying away from fatty foods is more disapline then anything ... you have to tell yourself that they are empty calories and substitute it with something healthy. Drinking lots of water will help curb your hunger as often times, when you think you are hungry it is really dehydration.
As for flat abs, that is one of the toughest goals and doing 1000 situps a day will never get you there because it's the fat on top that needs to be trimmed ... and, in most cases, it is the last place you will lose the access weight.