Its easy to figure out but tricky to stick with for many. Burn more calories than you consume and you'll lose weight but you dont want to loose muscle aswell, do you? too much cardio and sudden drop in calories can make the body eat its own protein stores, which incl the muscle so its wise to plan your routine out accordingly and read the great e-book's from Tom Venuto and Chris Aceto who are great in this field, look into it.
Lastly, folk can easily turn to things like clenbuterol ''clen'' to help them in this process but my advice is stay way from it and try doing things naturally. You could use supplements that help with fat burning but makesure they aren't the type like clen and dont have nasty sides or potential longterm health complications.