Develop new traditions. Create new traditions that incorporate customs from each family. You need to learn to negotiate as you work out these new alternatives. Even simple things like whether to have corn or sweet potatoes with Thanksgiving dinner will require compromise. Take time to talk.
Many blended families find it helpful to set aside a regular time when everyone gets together.
This time should not be used as a time for complaining or arguing, but for making sure everyone's voice is heard. It's especially important to involve older children in decisions that pertain to them. Forming a new family unit that meets each member's needs is a challenging task. It may be hard to believe you ever will be comfortable with one another. But, given time, your efforts can prove richly rewarding.