I hit a pleatau for around 6 months in my weight loss. And since I was weighing daily, I didn't notice it. I went to myfitnesspal.com (a free calorie spreadsheet) and began tracking my eating. The diet is the most important thing. I was surprised at how much junk I was eating, and how many extra calories I was having. It's very difficult to pull off around 1800-1900 calories a day for weight loss when you have a even an extra doughnut in your diet. But, its good to treat yourself in moderation.
After that , the weight started falling but after I corrected my eating and got leaner it was becoming much more difficult again. I didn't hit another pleatau, but, I had to change my excerise. 8 miles to the gym and back wasn't doing it anymore. So, I started HIIT (High Intensity Interval Training) 15 minutes a day, running one day, then rest the next, then bike doing it the next day, then rest the next, 3 times a week. From there on it was downhill and then I reached my goal.
For example, with biking, my body was very used to biking, so , it was easy. Doing HIIT running was extremely difficult. That was a different story. Doing HIIT with biking was also very difficult, but I only got my heartrate up to 80-85% biking, and 99% running. Apparently HIIT is good for 2 reasons: It doesn't take much time, and , the caloric "burn" is longer I've heard. Because you gave your body such a beating...
It's not easy, but if you can do it, and you watch your diet, you will most likely go thorugh your plateau. Best of luck to you.