You don't say how old they are, but here is some advice for toddlers up to 6/7 years old.
They are "Mommy Deaf" They probably hear you say "no" and "don't" about a thousand times a day, and they just don't listen anymore.
First start by guiding their bad behavior into positive outlets. Play games with them. Sing songs with them. Read stories to them. Once they know they have your attention, they will not need to act out to get it.
Set up a daily schedule with meals, snacks, activities with you, outside time, quiet time, housework time, and free play time. This can be any way you want, and times don't really matter. It's just important for your children to know that after snack time is housework time, and then it will be time to play outside. When they know that housework time or quiet time is coming, they will be more likely not to rebel against it.
Make some household rules. Let your children participate in this. Write them on a peice of posterboard in a positive way. For instance, instead of "No hitting," write, "We keep our hands to ourselves." Instead of "No running," write "We walk."
This is the hardest part, and it takes practice. Try to restrict yourself from saying "Don't" too much. Children hear only action words. So if you say "Don't run, Don't run," over and over all day, all they hear is "RUN, RUN, RUN" Try to say "We walk" instead. Say "We lower our voices" instead of "Don't shout." Say "Feet are for the floor," instead of "Don't stand on the couch." This really helps with young ones.
Give them options that make them feel in charge of their lives. "Do you want to go to the park or the library today?" "Do you want carrots or apples for a snack?" Small things make a big difference.
Use reflective listening. When you hear, "I don't want to clean up," respond with "I know you don't want to, but we all do our part to keep the house clean." When you hear, "You make me mad," respond with "I know you are angry, but I am your mother and I do what's best for you."
These are just a few things that have helped me with my very independent, rebellious five year old and with having a daycare in my home.