Do it gradually and make sure your metabolism is kept strong by including strength exercises. You might want to be more specific about your situation if you want better advice.
Add different/exercises to your routine got to give you body something esle to push itself too. If for losing weight add some good sprints and ofcourse you have to eat right but you have to find out for yourself whats your strengths and weaknesses because everyones different.
Whether the plateau is upward or downward, what you're doing has to be sound and consistent. Set up plans for each day to the point where it becomes natural.
