Every child is different in this regard.
Some kids need their hands held when they are young (though they should grow out of it as they get older, unless there's a problem afoot).
As a child, I actually performed worse when I had homework "help" -- intellectual boredom from work that was far too easy for me plus motor and RSI issues that impeded writing made doing it alone a lot smoother.
My 8yo son is kind of a middle ground. He has a work table in my office, and we do our work together -- meaning that I sit at the computer and do my own thing until he asks a question.
Have the right attitude.
Whatever your child's learning style and approach to homework, the most important thing is having and teaching the right attitudes to your child:
be aware of what is going on at all times so that you can help your child react to problems while they are still small and manageable
let your child know that his/her education is a high priority for you, so it will be for him/her
instead of taking a "perform or punish" stance, teach your child that everyone has trouble sometimes, and look for solutions as a team
if you find your child is having a pattern of school trouble, educate yourself on the possible causes and solutions -- don't count on overworked, underpaid school staff to suss it out