Sometimes the educational setting at home is not as structured as that at school. This is not necessarily a bad thing -- all you have to do is be creative in setting the tone for homework. Some kids can do homework in any setting, but most need a quiet place, somewhere in your home where there is not a lot of traffic to disturb them. Let them turn on some music and relax while they work. Homework doesn't have to be done at the kitchen table or completed while they are locked up in their room. A bean bag chair and clipboard can be just as effective as a school desk or a table.
Nobody wants to work and get nothing for it. Sometimes good grades are not enough to motivate young minds. Add an incentive to the homework ritual. This could be anything and it doesn't have to cost much. A favorite food or dessert during dinner is great for the food-motivated student. An hour with a videogame or a favorite television show can make a good reward for those who are visually motivated. If you have more than one child, just some planned time alone with a parent will not only be a good incentive but will help develop better inter-family relationships.
Homework is a part of your child's education as much as the work he completes at school. Make homework a habit by scheduling it into the afternoon and nighttime family routine. Have a place set aside for homework and a specific amount of time to do it in. An example would be to have the child come home, unwind with a snack and enjoy a little free time. At a specific time, the child must be in the designated homework area ready to work with everything needed to complete the task. As a parent, you must ensure that this happens to instill continuity, and soon it will become a habit.
If your child is struggling with homework and not getting anything done, sit down with her and make homework a game. See what she is doing and really get into the content of the assignment. For example, if she is doing math, time her to see how many problems she can get done in five minutes. If she gets four problems done, raise the bar and see if she can get six problems done in the next five minutes. Have a small reward if she makes it to the goal. If she does not make it, lower the goal until it is achievable.