1) Do not let him sleep in the afternoon. It is easier said than done...
first let him sleep till 10 or 11 or whatever time "he gets up himself" in the morning... keep him busy during the day time but do not let him indulge in any physical activity for a prolonged time..... then make ur nerves strong and no matter what it takes keep him awake during the day time.
2) after 3/4 pm he will be either a cry baby or a complaint baby... let him be..... keep him busy
3) after 8 pm switch off all or any TV at home.. take him to bed and keep him there...
it will take 2 to 3 days to work but it will undoubtedly work... the thing to remember is that kids when they get up late in the morning and then sleep in the afternoon are 100% fresh and charged up for next 10-12 hrs. on the other hand if your kids develop a habit of sleeping early at night and then getting up early in the morning as well the there is no harm if they sleep for an hr in the afternoon. if the above picture is not true then trouble is on its way.