Make time for each other. It's very hard when you have children to get away but remember that without your marriage you would not have the foundation of your family. Keep in mind that your marriage is just as important as your children. You're setting the example for your kids when it comes to good/bad relationships. So set a good example!
Make sure that your spouse knows that they are a priority in your life and not just another person in a schedule or scenario. They are important and life wouldn't be the same without them - make sure that they are aware of that! Don't assume!