Ok, so you've been following your workout plan for awhile now, and getting results. But suddenly, the scale is stuck, or your clothes just aren't fitting any better, or you're not seeing any more definition. What do you do?
The answer is, perhaps obviously, change. Once you've hit a plateau, it means your body has adjusted to whatever you're doing and become efficient at it. It doesn't need to physically change to keep it up, so it doesn't.
So the question is what to change? You have several options.
1) Up the intensity. If you've been taking leaisurely walks, try speed walking or tackling hills. If you've been at a level 3 ramp on the treadmill, bring it up to 4 or 5. Go faster and harder for whatever cardio activity you've been doing. And if you're not doing intervals yet, now is the time to start. (Intervals means working at alternating intensities - for example, very hard for 1 minute, medium for 2, repeat. This has been shown to be the most efficient way to lose fat thus far.)
2) Increase the weight you're lifting. Women: don't be afraid to get bulky. Long lean, toned bodies are built by lifting heavy weights, not doing 30 reps of a light weight. Really. Choose a weight you can lift with good form 8-10 times before you become completely worn out and unable to continue. Then do 2-3 sets with about 30 seconds of rest in between. Or do circuit training, where you do a different exercise right away instead of resting, then going back to the original exercise for additional sets. This way you make the most of your workout time and increase your calorie burn. As the weight you're using becomes easier to lift, increase it.
3) Do something entirely different. If you've been on the elliptical exclusively, try the treadmill and bike to switch things up. Try body weight or free weight exercises instead of weight machines (if you're not sure what to do, do the research, ask someone who knows, or hire a trainer). Try a new sport, martial art, or other physical activity. Make your body start to adapat to something new. This is how you get physical change.
4) Change your diet. You may need to decrease your calorie intake. Believe it or not, if you've been on a very low calorie diet, you meay need to eat more. Don't skip meals. Drink lots of water, 64+ ounces daily. You may need to increase your protein intake, or even your complex carbs. Watch your fat intake and try to get mainly the "good" unsaturated fats rather than saturated or trans fats (clue: anything that says hydrogenated oils has trans fat whether the label lists it or not, because it turns to trans fat in your body). If you're just not sure what to change or are completely overwhelmed, try seeing a nutritionist or dietician.
5) Take a break. If you're feeling sluggish, sore, injured or just not into your workout anymore despite doing lots of exercise, you might need a rest. Once you're able to tackle your workouts with a recovered body, you may start seeing good results again. People who are avid exercisers or athletes need to take about a week off every six months or so to fully recover and start fresh.
Hope this helps. Good luck!