D, what plan have you been following so far that's been working?
I know that changing up the exercise helps alot. Varying it, doing different things, trying weights if you've mainly be doing cardio/aerobic stuff, doing intervals w/the cardio stuff really jumps your metabolism around. Also the same for eating. Your body acclimates and adjusts and just gets used to the same old thing all the time. Sometimes it stinks how well the body adapts! It knows what to expect and what is expected from it.
Zig-zagging your calories keeps your body in a constant "guessing" state which translate into burning more calories. If you consistently eat say 1500 calories a day, try eating 1700 for a day or two then 1400 for a day, then 1600 for a day then 1300, etc. You get the idea. Also, eating every 3 hrs or so a combined good protein w/good carbs and fat will keep your blood sugar stable and the eating so frequently keeps your metabolism constantly working. You're constanly "stoking the fire" so to speak.
I'm sure others will be on w/suggestions too. Good luck and keep on posting. Oh, and reading through posts on here I've learned lots of info and tips.