1. Eat Enough. When trying to lose weight, make sure you're eating enough. That's right, enough. If you cut your calories too drastically, your body will compensate by slowing down your metabolism to conserve energy. It's getting ready for a prolonged period of starvation. If you're eating under 1,200 calories a day, consider changing your diet to eat more.
2. Smaller More Frequent Meals. If you're eating three large meals throughout the day, try changing to smaller, more frequent meals. After you eat a large meal, you'll probably be tired and not feel like doing anything. While you're not technically slowing down your metabolism, if you had been active rather than sit around after a large meal, your calorie expenditure would've been higher.
3. Build Muscle. Muscle is metabolically active tissue meaning that even if you aren't working out, it'll burn calories. To take advantage of this you need to have a workout that puts a priority on building muscle. Read more about strength training workouts.
4. Replace Fat With Muscle. Unlike muscle, fat tissue burns very few calories. It isn't metabolically active. Another priority that your workout needs to have is to get rid of fat stores and replace them with lean body mass (muscle). Read more about cardiovascular routines.
5. Exercise. When you exercise, your metabolism stays elevated for about 24 hours after you finish to help with recovery. Exercising is a good way to speed up your metabolism and burn more calories.