If you want an exceptionally effective method at burning fat, then start doing morning cardio! Keep the session relatively short and brief, and do it with intervals using ultra high intensity.
I'm not sure who, what, or where the idea is perpetuated from that you need to do hours of cardio on end to burn fat. That's absolutely false. I can't think of a better way to waste time than that. In fact, I'll explain later why long duration cardio is simply a waste of time. Don't get me wrong, of course it'll help you burn calories, after all you are doing hours of low impact exercises, but it's far from being the most efficient or effective method.
Let me share a little story about me and my family with you. I've been training, quite hard for the better part of 17 years now, since I was a young boy. So I'm quite fit, with a good body fat percentage. About three years ago, our first child (a baby girl) was born. during the time my wife was pregnant and up to a about 2 weeks after birth, I noticed for no particular reason that I was getting FAT! Well, I noticed that I was gaining fat around my waist area, while nothing has changed in my training or diet. So I was a bit alarmed, and thought to myself: "OMG... I'm getting old... Metabolism must be dying on me." =) I was 29 then. Fast forward 2 years, and our 2nd baby, a boy, was born, and what do you know, I experienced the same thing! I was accumulating fat around my mid section. What a disaster, I could hardly see my six pack. Okay, you're probably thinking, gee, it can't be that bad if you can still see your six pack Jim.
Anyway, I did some digging, and apparently there is this thing called Couvade, or "sympathetic pregnancy" that many men experience, where they experience a bunch of different "pregnancy sympathy" related symptoms, that's due to hormone changes. Luckily, the only symptom which I had was a bit of fat gain, especially around the mid section. So, I'm not getting too old, and my metabolism isn't dying on me. So, what I did was up my cardio intensity, and shifted my cardio sessions from day time to first thing in the morning. I had always known that morning cardio is the best, but due to daily time arrangements, it was a bit difficult to fit it in at the morning. But I was in crisis mode! And I absolutely had to get rid of the extra bit of fat I put on from pregnancy.... er... I mean from my wife's pregnancy. =)
Effective Ways to Lose Weight
Anyway, what I did was I increase my cardio training from 3 times a week to 4 to 5 times a week, and moved it up to first thing in the morning. The rest is history. I managed to burn off the extra fat, and became a six pack dad with 2 kids! Kidding aside, what I hope you get out of this is that morning cardio is exceptionally effective at burning fat. However, please keep in mind that I was in good shape and very fit to begin with, and my diet, training, and everything else was good a usual. So please do not think that morning cardio is going to be a magic bullet for you, that it's all that you have to do without making appropriate changes to improve your diet and exercising. Cardio is ONLY one aspect of a successful program.
So why does morning cardio work so well, and why do it first thing in the morning? When you wake up in the morning, depending on when you last ate, you've gone through roughly a 7 to 12 hour fasting period, and your muscle glycogen stores at this point is either low or depleted. During exercise, glycogen is the first source of energy burned, and fat after that. So when your glycogen stores are low, it won't take a whole lot to burn it all, and quickly begin mobilizing your fat stores as energy. This is precisely why I highly recommend morning cardio. Studies have confirmed this. One study with 14 well trained cyclists tested the effects of training with low muscle glycogen on fat metabolism, and found that while training with low muscle glycogen reduced training intensity, it significantly enhanced fat oxidation.  Other studies have also found that maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. 
So what's the best way to go about doing these morning cardio sessions? By far my favorite cardio exercise is the rowing machine. I have a concept 2 rower at home, so I hop on that first thing in the morning. However, any cardio exercise will do such as biking, treadmill, stair climber, or simply a jog or run outside. But here are the key points you must keep in mind:
- Keep the sessions short - about 16 to 25 minutes. No more than 30 minutes.
- Do it with ultra high intensity - the more intense the better. Shorter duration cardio sessions that involve very high intensity burn less calories during the duration of the workout, but these intense sessions work to elevate your metabolic rate long after you are finished, resulting in naturally high energy expenditure throughout the day.
- Do it in intervals - you simply cannot maintain peak intensity for say 20 minutes straight. Which is why you need to do it in intervals. For example, 2 minutes warmup, 1 minute 95% peak intensity, 30 seconds moderate intensity, 45 seconds 90% intensity, 1 minute moderate intensity, 20 seconds peak intensity, and so on. To keep things interesting, once awhile, I'll try to do 20 - 25 minutes of constant cardio at about 90 to 95% peak intensity. Now I say "I Try", whether I succeed or not is another story. =)
There you have it, my little spiel about morning cardio. It's a bit long, and I try to keep it short, but I had to get everything in there that was on my mind. As already said earlier, this is just one aspect of a successful fat loss program. You need to make sure other factors such as your diet and training are also in place to achieve the best fat loss results. I can wholeheartedly recommend Tom Venuto's Burn the Fat program for this purpose. I've had a copy myself for several years now, and the material, information, guidance, and help contained in that book is invaluable if you want to burn off fat. I've mentioned Tom's name and his Burn the Fat program many times before, because it's one of those things that I think is truly useful and helpful for losing fat.