dude, i've struggled for years to answer that question. well, i'm gonna have to say that i've found a really effective way to do so, and the best thing is that it really suits lifestyles, because i could tell, ok go the gym every day for 5 hours and sure you'll have ripped abs and so on. But for busy people, who have a life like me there's an easier way.
First , diet is the most important factor, I don't want to talk about the scientific facts, i would spend the whole day here. What you have to do is eat no carbs, no more than 50 grams (avoid sugar please) for 3 days, and drink a lot of water, and if possible try to eat often, and shut meals down at night. Don't you really worry about calories, you will find yourself eating less than usual, because avoiding carbs makes you feel full, really. But the MOST important thing here is your fourth day. Don't skip it, it's important. So 3 days of no carbs and then you have a day where you have to eat carbs, try to go with good carbs though, like non refined carbs. if not, don't worry, you can cheat, but it would be better to do it early in the day. you know brown rice, etc.. have a nice day with a big lasagna or soemthing, don't you think that you could skip this step, if you do so, your metabolism will go down, and it could be REALLY bad. and finally what i do before a go to bed, i workout, you know, pushups, pullups, i use dumbells, but since i like tone and not size, i don't do too much weight,, try to reach 30 reps and y go slow and smooth. That's it, to keep your muscles active and your metabolism high. Hoep it helps, you 'll find yourself much better, don't trust the scale, trust your eyes. good luck