Make a checklist of behaviors you expect. Be specific, such as say brush teeth for 2 minutes twice a day.

Write or print a chart.

1 shower daily

2 brush teeth twice daily

3 floss once daily

4 apply deodorant

5 work on school work for -- minutes - or if school is out read a book or magazine for 30 minutes each day

Then reward the behavior. You can give time to play video games or TV or telephone time or going to a movie.

It usually takes a few weeks to change behaviors. Your child also may challenge you but just don't give the rewards. No need to yell. You are the boss and that defiant creature living in your house is going to challenge you during the teen years.