Metabolism is the mechanism our body uses to break down the nutritional intake into nutrients some of which will be used to build muscle (anabolism) and some will turn into energy ready for the body to use (catabolism). The word metabolism, comes from the greek word "metabole" meaning change, essentially describing the "change" that happens to our food, once digestion has started.
The rate at which food breaks down into nutrients determines a "slow", "normal" or "fast" metabolism. No matter what sort of metabolism we might have inherited from our parents, one can always boost their metabolism in a number of ways.
1) Breakfast plays a crucial role to one's metabolism. In the morning metabolism is slowed down because of being asleep for duration of the previous night plus the fact that the stomach is essentially empty since last meal was many hours ago. Skipping breakfast will only slow your metabolism even further. A quality, high nutritional value breakfast including proteins, fibres, vitamins and carbs will not only boost your metabolism, but also prepare the stomach for the heavier meals to come.
2) Don't skip meals. Skipping a meal (or halving a meal to save calorie intake) signals the metabolism that times are getting "lean" so breaks are put on the fat-burning process to save energy for perhaps even "leaner" times. Now you know why even the in-between meals are equally important as the rest.
3) Build muscle. There is a controversy lately about how much muscle gain can impact one's metabolism and therefor their fat burning capability. Some studies show that an extra pound of muscle can burn up to 90 extra calories, others show that it is as low as 5-6 extra calories during rest. Whichever the case, big impact or not, the fact remains the same. There is an increase in the resting metabolic rate. And then again don't forget the calorie expenditure needed while trying to build muscle.
4) High Intensity & Interval Training. Any sort of physical activity (and by any I literally mean any...from raising a glass of water to the mouth, to running a marathon) there is a need for energy expenditure, therefor the burning of calories. Of course the expenditure differs from activity to activity. My personal favourite is High Intensity training and Interval training. Short duration, high intensity workout sessions have proven to be highly beneficial. Study has shown that oxygen intake by the muscle tissue remains at a much higher level even 48 hours after the session, as opposed to any sort of steady state training, which drops to normal just a couple of hours after the workout. I also apply this principle at any given opportunity (e.g. staircases...whenever you see one ahead, just run up. You'll be surprised at how effective a few seconds of intense muscle work, a few times a day, can be)