Cardio exercises are great for losing weight as long as their effectiveness in the lowering the fat percent is much lower than the exercises with weight lifting, and especially the combination of weight lifting and cardio. If you have not enough money and time, you can make the cardio exercises at home. You can jump rope, climb the stairs, run etc. if you have enough money, you can buy stationary bike, running track or something similar. But, it is better for losing weight if you run outdoors. For losing weight there are no best cardio exercises.source
If you like the fitness center for burning calories, do that. If you like to be more outside, always make the cardio exercises outdoors. The most important thing is to stick to your plan and to make the exercises you like. Many people entertain themselves and prefer exercises with low intensity, in order to keep the heart beats in the limits of burning calories. Besides the fact that in this way more calories are burn, there is no big difference in the number of calories that are burn during 24 hours between the exercises with low and high intensity.sourcesourcesourcesource
What is the effectiveness of the exercises? When the pulse starts to be with frequency of 130-180 beats, and then after some time the body starts to burn energy from the reserves. The body receives the exercises as extreme, and because it keeps the fat for years. The normal heart beat is about 60 beats a minute. The safety of the cardio exercises is between 130-180 heart beats.