Set aside time for homework. Make sure that your child knows that it is homework time and it is non negotiable.
Create an environment that is conducive to doing homework. It helps if there is a permanent space where children can do homework
Make sure that your child knows that the TV will be turned off during homework time.
Try to keep a bottle of water on the homework table and encourage your child to drink, to keep the brain hydrated.
Be available to answer questions, but make sure you do not do your child's homework for them.
If your child is working for long periods of time, stop for a hot drink or fruit break. If they are showing signs of fatigue, put some lively music on for a couple of minutes to perk them up.
You could play classical music softly in the background or a motivational affirmation CD such as Believe and Achieve
If your child is studying at their computer for long periods of time, make sure they close their eyes, take a walk or breathe in some fresh air.