need to loose weight

im 9stones and need to loose weight i go to the gym evryday starting for this week diet. i burn 400 calories a day and have plenty of water juice, what else i need to do to loose a stone? pls help

First off, you do not want to lose weight, you want to lose fat.  You can lose fat while gaining weight so change your thinking right now.  Secondly, you say you drink juice.  If you are using it as a pre or post-workout creatine or protein uptake aid, then drink it, but it has little use after that.  Fruit juice is like a coke with vitamin c added, it raises your blood sugar rapidly which raises your body's insulin levels and causes your body to store fat.  Try to get your fruit with the fiber (whole) and leave the juices to people that don't care about themselves.
For your workouts, keep the rest periods short to keep the heartrate up, use weights to gain muscle and cardio to raise endurance so that you can lift more weights.  Muscle mass burns fat much more efficiently that fat does.  Eat heavier in the morning and taper off the calories throughout the day.  Eat every 3 to 4 hours, but keep the meals 500 calories and under if possible.