1. Shake up your calorie intake -- don't eat the same amount of calories everyday. Eat 1,600 one day, 2,100 the next. That will give your metabolism a workout.
2. Change up your exercise routine! Don't just get on the elliptical for half an hour - Look for group classes at your gym and always add weight training.
3. Switch up your snacks! If you're eating a granola bar or some sort of carbohydrate for a mid-day snack, try some thing with protein. That will keep you feeling fuller and trick your nutrient intake and your metabolism.
No matter what - just keep trying! If you have already fallen off your resolution wagon, make a point to start again this weekend.