Metabolism is nearly entirely dependant on the individual's genetics. Altering basic metabolism is nearly unheard of, probably impossible. Everyone is advised to exercise and eat well but if you have a slow metabolism, that's how your body should naturally work. It can't be changed.

Increasing your meals from the usual 3, to 5-6 times a day but in smaller portions increases your metabolic rate (of course, as the one above me stated, it isn't something that could completely overcome your genetics). So, instead of eating a big lunch and a big dinner, eat small meals just enough to keep you satisfied for a few (2-4) hours. High intensity and aerobic exercises also increase your metabolic rate (not permanently). What occurs is that your metabolic rate increases during your recovery period (energy debt) within the hours after your work outs in your body's attempt to refill used energy stores, hormones running through your body, etc.

Simply, don't be lead into the false belief of losing weight by ONLY attempting to increase your metabolic rate. You may increase it via the methods I stated above, but in which what you are eating should be monitored, and ensure your work outs burn your fats on top of that.