This is a challenging question as many parents, including myself, have a history of "overseeing" homework and study habits in order to ensure that their child has completed work for school. Yet, as our kids move in to the older grades, we need to give them more independence AND responsibility. This is tough!
Some techniques could include a contract between parent and child. Essentially outlining what is expected, what are reasonable parameters (eg. Will finish homework within two hours from completion of dinner and before going online with friends) and any consequences (loss of privileges).