Even when the parent disappoints the child and the child complains to the stepparent, do not put down the parent. Look for ways to form a civil relationship with your spouse's ex. Put the brakes on sibling rivalry. Help reduce the minor scrapes between your children and your spouse's kids by being a fair, consistent disciplinarian. Be aware that you and your spouse will each have your own style of discipline, but try to find some middle ground and then support one another.
Kids then know what to expect.
Be honest about money. Nothing drives two people apart like financial disagreements, especially when kids are involved. It is crucial for people with children to be honest about income and expenses, including child support. Talk things out as a group. Discuss household rules and disciplinary issues and air your differences in family meetings.